How to: 4.10 install and differential overhaul -

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Old 12-23-2010, 02:01 AM   #1
Thread Starter
Join Date: Sep 2009
Location: TX
Posts: 41
Post How to: 4.10 install and differential overhaul

First things first, I realize that I am not a professional mechanic, in fact, I'm just some kid who likes to work on his car. I recognize that my install may not be 100% correct and I am willing to take advice from any of the gurus out there on how I should have done something differently. Secondly, I'm no taco-bill. This is my first write up and I did the best I could with taking pictures and getting the work done at the same time. As a result, not all of my pictures are as good as I would like them to be. I will try to make things as clear as possible, but if there is any part that gets confusing, let me know and I will try to edit it and make it clear. I plan on trying to write this for people like me who want to do this install themselves, but have absolutely no working knowledge of a differential. But anyways, on to the job at hand.

Pre Install

1. Like everyone, I vacillated between 4.10 and 3.73. I have a manual. I went with 4.10 and I don't regret it at all even though I drive about 10 miles on the highway everyday to school. That's all I have to say about that whole debate.

2. Was I nervous about doing this work? yes. very. But, (and this isn't supposed to sound as conceited as it's inevitably going to) I knew that I was probably about as smart as mechanic Joe who was going to handle this had I chosen to have it professionally installed. But more importantly, I knew that I was going care more than mechanic Joe because it's my car and I want it done right the first time. I'm not trying to say that there aren't fantastic mechanics out there that do outstanding work, I'm just trying to tell you that you are more than likely capable of doing this install if you have a little bit of intelligence, decent determination, and a $hit ton of patience.

3. I learned what I know through the internet. I did a lot of research and pretty much hoped for the best. If you have a friend who has done this before, take advantage of that.

4. DO NOT TRY TO GET BY WITHOUT THE TOOLS THAT YOU NEED. Being 17 and foolish I figured I could get by without this or that and all it ended up doing was stalling my progress when I realized that it was 10:00 on Saturday or Sunday and I needed a specialty tool. There are certain points where you have no option but to spend some money on tools. Luckily for me, I'm still under the wing of my parents and was offered the support of their credit card when it came to tools, but I still tried to find the best deals that I could. My suggestion would be to get what you need off of ebay or from Harbor Freight Tools. It saved me a huge amount of money. Harbor Freight may not have the highest quality stuff, but realistically, I'm only using this tool once so there's no point in paying $60 for a professional bearing separator when HF has it for $12.

5. There are some steps that I just recommend having a shop do. The biggest one is removing the old carrier bearings. If you have low mileage and don't plan on changing the bearings, consider yourself lucky because I was but I'll talk about that when I get there.

6. If you've never done a gear install before, or even if you have, I would recommend completely removing the rear axle from the car. That's what I did and I have never made a better decision in my life. unless you're working on a garage lift, I really don't see how this can even be done with the axle still in the car, so just go ahead and take it off because it's really not that hard.

7. At the time of my install my car had around 65,000 miles so I decided to go ahead and replace all of the bearing, races and seals in the differential. I also replaced the axle oil seals. I don't know why I didn't replace the axle bearings, I just decided not to. So this write up will cover all of that, not strictly replacing the gears. I would recommend having complete install kit because even if you don't plan on replacing the bearings because its always nice to have a part if you break it. Also, having the old inner pinion bearing and being able to trash it made setting the pinion depth WAY easier. I will explain later.

8. So far I've put about 3,000 miles on the new gears, and I haven't had any issues. I have a slightly louder whine from the rear end when engine braking, but I would imagine that this is normal because I set the gear mesh tighter than the old gears (The old gears seemed strangely loose)

9.Expect to have the car out of commission for longer than a weekend. If it's your daily driver, don't expect to get the job done in a weekend. My car was out of commission for 1 week, but that's somewhat attributed to the fact that I didn't have all of the tools that I needed, I found out that I needed parts, and I was in school from 8-3. So it doesn't have to take nearly that long, but don't plan on it being a quick weekend project.

10. Wear clothes that you are okay with throwing away when you are finished. I wore the same shirt and shorts the whole time I worked and I smelled aweful, but at the end I only had to throw away 1 shirt and 1 pair of shorts. Don't plan on sticking these clothes in the washing machine because it will give the washing machine the same aweful sulfur compound smell that the differential oil has.


1. Ring gear and pinion. I think it makes sense to get the FRPP gears, but if you really want motive's 3.90 or something then that's your decision.

2. Gear installation shim and bearing kit -- the bearings aren't necessary if you don't plan on replacing any bearings but if you don't get a bearing kit, I would recommend buying a new inner pinion bearing and race so that you can shave the old one. I'll explain what I mean when i get there. I got this part from Brenspeed who I ordered the gears from. I think that FRPP also makes an install kit, but I got the motive kit because that's what Brenspeed sells.

1. inner pinion bearing and race
2. carrier bearing and race
3. carrier bearing and race
4. outer pinion bearing and race
5. carrier shims
6. pinion shims
7. ring gear bolts
8. crush collar
9. pinion nut
10. differential housing gasket
11. pinion oil seal
12. gear marking compound

3. Pinion shaft retaining bolt -- I didn't have this problem, but I have heard about this part ending up bent after removal.

4. Axle oil seals -- I got these from the dealership and they're not too expensive. My thought process was that I may as well do it because it's not often that I have the axles out and the seals exposed.

5. new inner pinion gears and side gears -- I needed these because when I broke everything down I found that one of the side gears had a chipped tooth, so I picked up new ones from the dealership.


1. I'm assuming that if you are thinking about this install, you own a decent set of basic hand tools. If you donít, you're really not gonna get very far.

2. Also necessary is a decent click style torque wrench. I would probably recommend both a 5/8" and 1/2" drive but you can make that call yourself. Just make sure it can reach the torque specs required.

3. Dial Indicator -- used to measure pinion head thickness and shim thickness. it turned out helpful for setting pinion depth and essential for setting backlash.
My dad is an orthodontist and so he had a dial indicator at his office, but these are pretty easy to find. ebay is the best bet if you want to save some money.

4. Bearing separator -- essential for removing inner pinion bearing and proved pretty useful other places. I thought I could get by without it. I was wrong.
This I bought from Harbor Freight. One because I thought I could do without it and didn't have time to order it, and second because I had absolutely no idea what size to order. Get the large one form harbor freight, the link is below.

5. Dial Indicator with magnetic base -- this is absolutely necessary! it is used for measuring backlash, which probably the most important measurement of the whole install.
At first this looked like it was going to be an absurdly expensive tool, but I bought it off of ebay for about $10 and it was brand new.

6. 1/4" drive beam style in-lb torque wrench -- essential for measuring bearing preload.
this was the most expensive tool by far. the one that I bought is made by Park Tools, which is actually a bicycle tool company. If you go to your local bike shop they might have one they would be willing to lend you, but you'll just have to see. I got mine off ebay and since my dad and I are big into mountain biking he was willing to front the bill (oh joy).

7. Bearing race and seal driver -- for installing bearing races and oil seals (obviously).
I bought this off of ebay which was considerably less expensive but it still wasn't really cheap. It can also be bought at harbor freight tools for about $35.

8. 2 or 3 jaw gear puller -- has many uses
I rented this form the local auto zone. It was a reversible 2 or 3 jaw puller and it suited my needs. To rent it you had to pay for the tool and when you brought it back in good shape, they would give you a full refund. pretty sweet.

9. Gear marking compound -- used to check the wear pattern and determine proper pinion depth and gear mesh.
This came with my install kit and I would imagine that it comes with most. If not, a google search will probably suffice.

10. punches for punching out bearing races.
I Just had these around the house but they can be found at Home Depot or any hardware store I'm sure.

11. breaker bar, probably 1/2" drive -- used to turn pinion nut.
This can be had at any hardware store and I'm sure you could save a few bucks by buying it off ebay or something.

12. metal pipe -- okay, so this is hard to explain, but what you need one metal pipe to place over the breaker bar when installing the pinion nut, because there is a crush collar that needs to be crushed and that takes a ton of leverage. another piece of metal will need to be used to hold the pinion in place while turning the nut. I accomplished this by taking a scrap piece of metal tube that was lying around the house and getting a local shop to drill 2 holes in it with their drill press. I then used the bolts that hold the pinion flange to the drive shaft and inserted then through the metal pipe and into the pinion flange. To visualize this watch the youtube video below. It also shows how to check bearing preload (which is what you need the in-lb torque wrench for).
you can see he had about 2.5 ft as his lever arm in that clip and really had to pull. I used pipe that was about 5.5 ft long and it made things much easier.

13. 1/2" pry bar -- just came in handy. to make a long story short, I ran into a guy at Harbor Freight that only did diff work and he said that he gets carrier bearings off just with two pry bars, so I got two. It didn't work for getting the carrier bearings off, but they came in handy getting the S-spring back in.

14. axle bearing puller -- used it to remove the axle oil seals. It pulls the bearing out too but they're easy to put back in.
I also rented this from the local shop.

15. slide hammer -- attaches to the axle bearing puller to actually be able to pound the bearings out.
I rented it from the same place.

NOTE: if you don't plan on removing the axle oil seals, then #14 and #15 don't apply to you.

At this point I can see why you might feel a bit overwhelmed by the number of tools that you need and that you may be growing impatient with how much I'm writing, but the tools list isn't as bad as it seems, and I guess you just have to get over my writing.

The Basics of a differential

This is for people who are like me and don't know the first thing about differentials. If you already know the internal parts and workings, then you can skip over this.

For those who are interested, this video is an excellent tutorial on how a differential works. It's also a nice simplified picture of the internals of a diff.

Internal Parts

The four major components of the differential are:

1. The differential housing (includes axle tubes in our mustangs)
2. The pinion
3. the ring gear
4. The carrier

1. Differential housing

1. Carrier bearing Bore
2. Bearing cap mating surface
3. Gear oil slinger -- brings oil to the outer pinion bearing
4. pinion bearing bores -- the pinion will insert through that tunnel
5. differential oil fill plug
6. this isn't my picture, and the newer housings do not have these protrusions. the newer housings have a single protrusion from the center of the diff casing that attaches to the Upper Control Arm
7. beginning of the axle tubes

2. The Pinion
Pinion assembled (obviously it's not in the housing)

Pinion disassembled

3. The ring gear
the ring gear is pretty simple. It bolts to the carrier with 10 bolts.

4. The carrier
The carrier is the most intricate part of the differential. It houses the parts that make the differential, well, differentiate.

carrier assembled in housing: (in this picture the axles and the pinion shaft have already been removed)

1. ring rear
2. pinion head (way down there in the housing at the bottom of the picture)
3. Pinion gears -- these are held in the carrier by the pinion shaft and technically are the gears that drive the axles. the other pinion gear is the gear opposite #3
4. side gears -- These are the gears attached to the axles via splines. the 3 tabs to the right of the number 4 are the tabs of the friction discs. The friction discs sit between the side gear and the carrier wall. There is the same thing on the opposite side of the carrier, but it is hidden behind the ring gear in this picture. between the side gears is the S-spring.
5. This is the carrier itself
6. carrier bearing caps

carrier disassembled:

1. Differential carrier
2. Traction Loc assembly (this includes the clutch discs and the splined steel discs
3. side gears -- the splines are facing up, the teeth of the gears are down. if they were on the ends of the axles, the axles would be sticking up in the air
4. carrier bearings -- still on the ends of the carrier and were a PITA to get off
5. carrier bearing races
6. carrier shims -- the total thickness of these shims determines how tightly the carrier sits in the bearing bores of the housing. The shims are placed between the bearing race and the side of the housing and are secured by the carrier bearing caps. how thick one shim is compared to the other determines how deeply the ring gear and pinion teeth mesh which is called backlash, I'll explain more later, but for now we'll just say that they're very important.

Bearing end caps and pinion shaft:

more disassembled parts:

I believe that I have covered most of the information not concerning the actual process of installation. As I said at the top, please tell me if I have missed something or if something is not clear. It is hard to know if I have been clear in my explanations or not, because I have seen it have written everything, so it makes sense in my head. Also, I must also tell you that it is very, very hard to visualize how exactly everything is going together until you just get in there and start pulling things apart, so if it isn't 100% clear, that's probably okay. Anyways, on to the fun part...

Rear Axle Removal

Even though it might seem like a pain, just go ahead and take it out. You'll probably be glad to not work over your head for hours on end, and it's much safer to not be under the car.

This will require more than one person!! Get three people if you can. (two to balance the axle on the jack while one person mans the jack)

Keep track of which bolts are which!! I placed them in Ziploc containers and labeled, but do whatever works for you.

1. Jack up the rear of the car and put it on stands. You'll end up needing the jack for letting down the axle when you remove it.

2. remove the wheels

3. Remove the 2 13mm bolts holding the caliper to the caliper mount. DO NOT LET THE CALIER HANG BY THE BRAKE LINE! hang the caliper with a hanger or some other contraption

4. Remove the 2 15mm bolts securing the caliper mount to the axle. These are located on the back side of the mount. After this you can simply remove the brake rotors from the wheel studs.

5. You may realize that there is a wire running from the end of the axle and towards the front of the car. This will need to be unplugged in order to completely remove the axle. There is a place to unplug it about 12" from the axle end of the wire. There's also a zip tie somewhere along that wire that secures it to the lower control arm and needs to be cut.

6. remove the two nuts attaching the end of the sway bar to the axle
view from rear of car:

close up from front of car:

7. remove the axle ends of the lower control arms. It's easier to see the location of the bolts from the reflection rather than the actual image, so that's why there are arrows pointing at the reflection.

8. mark the relationship between the pinion flange and the drive shaft and then remove the 6 bolts the connect the DS to the flange.

9. remove the axle side of the panhard bar. The picture shows that both ends are connected to the axle, but only the driver's side is. This is the only step that does not need to be repeated for each side.

10. Remove the axle side of the shocks. When you remove the shocks, you also be able to remove the springs from their perches. At this point it is also probably a good idea to place a jack under the differential in order to support its weight, because the axle will only be held up by the upper control arm.

11. Remove the axle end of the upper control arm. you will need to have the jack placed under the differential and you will need another person balancing the axle on the jack. when you remove the bolt, the axle will not only want to tip side to side, but it will also want to roll towards the front of the car, so make sure the person balancing is prepared for that.

12. Now you can finally lower the axle out of the car (assuming that I haven't forgotten anything). I placed the axle on a stand that my dad threw together and I have to say, I think it is a necessity. Below is a picture of the stand that I used, but it doesn't really have to be anything too fancy.

Congrats you have finally come to the point where you get to open up the differential! Also a congrats on being able to put up with this write up for so long! So now, the fun part.
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Old 12-23-2010, 02:02 AM   #2
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Join Date: Sep 2009
Location: TX
Posts: 41

The disassembly

At this point it would probably be a good idea to invest in a box of latex or nitrile gloves, because the differential fluid smells awful, and it is very difficult to get off of your hands. Also, it becomes vital that you wear some clothes that you have no intention of ever wearing again.

Most of the pictures that I'll be using are from the re-assembly process because everything is clean and actually visible. That's why my ring gear is covered in yellow marking compound.

1. place a plastic container underneath the differential and remove the 10 bolts securing the differential housing cover. Pry open the bottom of the differential housing cover with a screw driver and let the oil drain into the container.

2. Continue to pry the housing cover off until it is completely removed. Let the oil all drip out. You'll end up with something looking like this:

3. remove the pinion shaft retaining bolt

4. remove the pinion shaft. For me the pinion shaft simply slid out, but I have heard that some take some pounding to get out. I got mine out by pushing it slightly in, then rotating the carrier to be able to pull the shaft out of the other side *DO NOT PUSH THE SHAFT IN TOO FAR* if you do, you might not be able to rotate the carrier because the shaft contacts the walls of the housing. Once the pinion shaft is removed, the pinion gears will spin out if rotated, and could fall into the bottom of the housing. Itís not a huge deal, but I would probably just avoid rotating them.

5. Remove the C-clips that hold the axles in place with a pair of needle nose pliers. You can gain access to these by pushing the axles in towards each other. Remove the axles and place them into the wheels (just put the wheel studs through the wheels)

6. remove the 4 bolts of the carrier bearing end caps. make sure you distinguish right from left because you need to re-install them on the same side

7. gently lift the carrier out of the housing. I was able to simply lift it out by grabbing the ring gear, but you may need to pry it out with a pry bar or large screw driver. Note: when you lift the carrier out, the bearing races will fall off of the bearings so make sure you catch them and keep them with their appropriate side. The carrier shims will also want to fall out of the bearing bores and into the bottom of the housing so make sure you somehow keep them separated with their appropriate sides after this you will end up with this:

8. remove the pinion nut. Unless you are using an impact wrench, you will need to use that metal bar with two holes so that you can hold the pinion flange still while you loosen the nut. Simply place 2 of the bolts that hold the drive shaft to the flange through the metal bar and screw them into the flange.

9. pull off the pinion flange with the jaw puller. You will end up with this:

10. at this point nothing is holding the pinion in place other than the outer pinion bearing. Hit the end of the pinion (the threads that you see sticking up in the picture above) with a dead blow hammer, or just cover it in a towel and hit it with a regular hammer. It takes a good amount of hammering. I couldn't actually hit it hard enough with a standard size hammer, so I used a 10 lb soil compactor and gave it a few blows. it fell right out and no harm was done, so don't be afraid to wail on it.
11. Now all that is left is the inner and outer pinion bearing races. If you look at them, you will see that there are two recessed areas, one on each side of the race that is perfect for resting a punch to hammer away at the race. Here is a picture of the recesses:

12. Now, to continue with further disassembly of the carrier: remove the S-spring. you can use whatever you deem fit to tap out the s-spring, just be sure that the side and pinion gears do not get the impact of your tapping. Once the spring is partially out, it will contact the ring gear, so I bent it up over the ring and continued tapping it out.

13. Now rotate the pinion gears and they should spin out of the carrier. The pinion gears have washers on the back sides of them, so be sure to keep track of them.

When the pinion gears are removed, the side gears will fall towards each other. Remove them one at a time to make sure that you do not lose the traction loc assembly.

*keep track of which side gear is which so that it can be re installed on the same side*

14. remove the 10 ring gear bolts. I placed the metal pipe through the center of the carrier and had my dad hold it still while I loosened the bolts. If you have an impact wrench, you can probably just pop them off with that.

15. hit the back side of the ring gear with a dead blow hammer until it falls off of the carrier.

16. Carrier bearing removal. This was by far and away the most frustrating part of the entire install. If I was going to do it again, I would find a shop that is willing to pull the bearings off with the proper tool and save myself the headache. There are two recesses in the carrier below the bearings that must fit a very specialized and very strong jaw puller that ford has, but that's just speculation. So my advice is to take it either to ford and see if my speculation is correct, or take it to a driveline shop and have them remove the bearings. BUT, if you are determined to do this yourself, I will walk you through what I did, but also be warned that I had to use a special miniature high speed dremmel which is technically a dental tool, so my dad has one at his office, but still, this was a PITA.

1. First I used a 3" air cutting tool to cut through the roller bearing cage. Then remove the cage and all of the rollers.

2. You will be left with just the inner bearing race still pressed onto the carrier

3. I had read and thought that you could set up the bearing separator on the top lip of the inner race, then use the jaw puller to pull the race off, but I thought it was sketchy looking at how little bite the bearing separator had, but here's some pictures anyways:

There is a large socket placed on the end of the gear puller in the above picture. The socket contacts the inner wall of the carrier so that the puller has something to pull against. I had no luck with this. I had heard that if you cut a slit in the inner race then pull it off with the jaw puller that it helps, but this didn't work for me either. I don't know if it would help to heat up the race with a torch, but I can't imagine it would hurt either, so you can give it a try if you'd like.

Another method that a driveline mechanic told me in Harbor Freight was to get two pry bars and place them in the recesses on either side of the race and pry it off, but that was hopeless. Here are the recesses that I keep talking about:

4. The method that actually worked for me involved this:

I used this high speed dremmel to cut a narrow slit in the inner race, and once the slit became deep enough, the races popped open slightly and cold be pulled off with my hands. On one, I dremmeled into it, then I placed a wedge into the slit and hammered the wedge and that popped the race open. It was very difficult to dremmel into the race and to know how deep to go so that you would not knick the bearing seat, but I was fortunate enough to not do any damage to the carrier.

I assure you that this process was time consuming and frustrating, I got to it on a Sunday and had no option but to try to get it done myself. So I'll say again JUST LET SOMEONE ELSE DO THIS STEP. I don't know exactly where to go to have this done because I didn't look into it, but I'm sure you could call around to some local shops.

17. Now the carrier is disassembled, so now on to the pinion. Place the bearing separator between the pinion head and the inner pinion bearing. Then simply hammer the under side of the bearing separator.

Cleaning and Measuring

1. using a degreaser and a standard kitchen scrubber, give all of the parts a good clean. Make sure that in the process you don't lose track of which parts go where, for example, make sure that when you're cleaning the side gears you keep track of which one is which. I don't imagine that it would necessarily cause any major problems to change them, but I also don't think that it's a bad idea to put everything back where it was.

2. Now a few measurements will need to be taken with your dial indicator.
The first measurement is to determine the pinion depth. There are very precise and specialized, but also very expensive tools for doing this the "right way" but most people don't want to spend $100 on a pinion depth set up tool, to only use it once, so I'm going to go through the unofficial wallet friendly method.
First is the thickness of the old pinion head with the shim that was underneath the inner pinion bearing, then measure the thickness of the new pinion head. Subtract the thickness of the old pinion head and shim from the thickness of the new pinion head, and you will have the thickness of the shim that needs to be placed on the new pinion head for the depth of the new pinion to be the same as the depth of the old pinion.

Here are my measurements:
Old pinion head and shim: 1.896"
New pinion head: 1.888"
Therefore, the shim that I need is 1.896 - 1.888 or about 0.010"

Although most people say that this method worked perfectly for them, I found when I checked the gear mesh that I needed a thicker shim. But it was still a good place to start.
3. next measure the thickness of both the right and the left carrier shim and write them down.

These were my measurements:
Driver's side shim: 0.277"
Passenger's side shim: 0.262"
Sum of left and right: 0.539"

4. Also measure the thickness of the old inner pinion bearing and race, and the new pinion bearing and race to make sure that they are the same thickness, because the thickness of the bearing would effect the pinion depth. If they are not the same, take that into consideration with your shim thickness calculation. Mine were the same size and I canít imagine that a decent install kit would give a different sized bearing, but hey, you never know.
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Old 12-23-2010, 02:03 AM   #3
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Join Date: Sep 2009
Location: TX
Posts: 41

Re-Installation ... finally

1. Let's start with the ring gear. The only difficult part about getting the ring gear on is making sure that the 10 bolt holes are aligned as you press the ring onto its perch. I would suggest using some sort of long bolt, maybe two of them and line them up so that when you seat the gear, the holes in the carrier line up with the holes in the gear. Like so:

But anyways, the first thing that you need to do is lightly sand the surface of the carrier that the ring gear will seat against and the back side of the ring where it seats against the carrier in order to insure a perfectly flat mating surface. I used a sanding stone to accomplish this

Next I placed the ring gear in a pot of hot water in order for it to expand slightly. I then pulled the ring gear out of the hot water (using thick rubber kitchen gloves) and placed it over the carrier while making sure that the bolt holes were lined up. It takes some force to press it over the carrier, but it doesn't need to be seated completely by hand. Instead, pull the gear into position by installing 5 of the 10 bolts. After the ring is completely seated, remove the 5 bolts that you just installed

The reason that I did not leave the bolts installed is because I wanted to give the water in the bolt holes time to dry so that nothing would rust over time.

2. Install the carrier bearings while you wait for the water to dry. Luckily, the carrier bearing installation was MUCH easier than the removal.

1. Start by heating the bearings in boiling water

2. I lubricated the bearing seat with some bike lube that I had around the house. I don't know how much it helped, but I figured that it couldn't hurt.

3. Then I pulled the bearings out of the water (using tongs and gloves) and placed them over the bearing seat (make sure they're on the right way)

4. Seat the bearing straight and pound it on using the bearing race and seal driver.

5. The bearing will eventually be seated flush with the top of the carrier, but it needs to be seated further. The bearing driver can't get it any farther because the lip of the carrier actually sticks above the inner race about 1/8th of an inch when the bearing is fully seated, so I improvised. I adjusted the bearing separator so that the inner diameter of the separator rested on the inner bearing race, but not on the carrier lip, then I placed a large metal chisel over the center opening in the bearing separator to act as a surface to pound on and gave it a nice whack with a hammer.

in this picture you can see three concentric rings, the inner most ring is the carrier, the second ring is the inner race, and the third is the roller bearing cage.

Then I placed the chisel

Then I hit the middle of the chisel pretty hard with a hammer. If you tap it lightly then you just have to readjust the whole set up because it bounces off after you hit it, so just give it a whack. There shouldn't be any space between the bottom of the inner carrier bearing race and the carrier bearing seat when the bearing is fully seated.

Repeat this process for the other carrier bearing.

3. Next install the ring gear bolts. Install these bolts with thread locker and hand tighten all 10 of them, then torque them progressively in a star pattern. The torque progression should be 20 ft-lbs, then 40ft-lbs, 60ft-lbs, and finally 85ft-lbs. remember to torque in a star pattern. Also, I placed my metal pipe through the center of the carrier to hold it stationary as I torqued the bolts.

4. Next re-install the pinion gears and the side gears.
1. The first thing to look at is the traction loc set up which is the series of splined steel discs and the friction clutch plates.

There are two different stacking orders for the traction loc that I have seen. First is the set up that comes from ford. Which is: shim, friction disc, 2 steel splined discs, friction disc, 2 steel splined discs, friction disc, side gear.

The other is something that I found on one of the install websites that I found and the author says that he found it on the internet as an "upgraded" stacking order, but I can't say anything about the validity of this statement. The order is: shim, friction disc, 1 steel splined disc, friction disc, 1 steel splined disc, friction disc, 1 steel splined disc, friction disc, side gear.

You will notice that in the alternate order you use fewer splined steel discs and one more friction disc. My install kit did not come with new friction discs and they were very expensive to buy from ford, so I did not have the option of using 4 friction discs. If you buy a rebuild kit, you will still need to re-use one of the old friction discs to have 4 on each side gear. I don't know whether or not there are positives or negatives about either stacking order, but I stuck with the ford factory setup.

Another thing that I did not have in my installation kit is new traction loc shims, which determine how tightly the 4 gears mesh. I don’t know what difference the tightness makes, if someone does, feel free to chime in. Even if I did know what difference it makes, I didn't have the shims to adjust it, so I put it all back how it was.

When I pulled the side gears out, I found that one of them had a broken tooth, so I replaced it and it wasn't a huge deal.

2. After deciding which stacking order you would like, stack the traction loc assembly on the back of the side gears

If you have a rebuild kit that included new shims of different sizes, start with trying to install the thickest shim offered, which is usually about 0.045"

3. place the side gear assembly into the "bottom" of the carrier, with the tabs of the friction discs lined up to fall into the slots in the carrier. If you have kept track of it, install the side gears back into the sides that they came out of.

4. Place the other side gear into the "top" of the housing in the same way and hold it in place with your hand.


Place the pinion gears directly opposite each other between the two side gears. To make sure they are lined up, look through the holes in the center of the pinion gears and sight that they are lined up.

Rotate the pinion gears into place.

Check that they are lined up by looking through the pinion shaft bore. If they are not, remove them, realign them, and rotate them back into place. If you sight the alignment before rotating them into place it can save you some time.

Because my install kit did not come with new shims or new friction discs, I reused the old friction discs and shims on the side gears. I called ford about getting new friction discs, but they were incredibly expensive and the parts department said that if the friction discs still had a decent amount of clutch pad remaining that it really wasn't necessary to replace them, so I didn't. Because I reused the old setup, I had no problems simply rotating the pinion gears in place with my hands. If I was going to do this again I probably would have just paid for the new friction discs, but c'est la vie. If you have the option (i.e. your install kit provided the shims), use the thickest shim offered on the side gears (typically .045"), and try to install the pinion gears. You may find that you cannot rotate the pinion gears in by hand, but that's okay. Place the gears opposite each other and lightly tap on the pinion gear with a punch and hammer to rotate them into place.

Don't hammer excessively, but don't give up with the first slight tap. If you find that you cannot get the pinion gears in place, drop down to the next smallest shim on the side gears and try again.

5. Re-install the S-spring. I had some difficulty with this step, but just be patient and it will eventually go in. The reason that installing the S-spring can be somewhat difficult is because the ring gear prevents you from getting the desired "angle of entry" if you will. As you upgrade to a taller gear ratio, the ring gear actually gets thicker, making the minimum angle of entry greater, if that makes any sense. Basically, you have to distort or compress the spring in order to get it to install and the thicker the ring gear, the more distortion or compression you need to get it in.

What I did was I used a pry bar leveraged against the ring gear to distort the "front edge" of the S-spring as a tapped the spring into place with a hammer.

This process is probably easier with two people, and the hardest part is getting the spring started. Remember which way the spring is supposed to be installed. I say this because I had to double check. It should end up looking like this:

6. next install the pinion bearing races into the differential housing. What I did was I placed the races into the bore and placed the old bearing into the new race.

Then I used the bearing race and seal driver to hammer against the old bearing.

Outer pinion bearing race fully seated

I then repeated the process for the inner pinion bearing race. For me the outer pinion bearing race went in without issue, but the inner bearing took time and a whole lot of pounding. Again I lubricated the bearing bores, and again I don't know how much it helped, but it can't hurt.

Inner pinion bearing race:

7. lubricate the new outer pinion bearing and place it in the race.

8. put the pinion oil seal in its place and drive it in with the seal driver. be careful not to damage the oil seal.

9. replace the axle oil seals. Apparently oil seal pullers are capable of getting these seals out, but either I'm not smart enough to use one or the seals are in way too tight to get out with a little hook on the end of a bar, so what I did was I rented an axle bearing puller and a slide hammer and pulled out the whole axle bearing and seal. Then I hammered the bearing back in place and replaced the seal.

Removing the bearing and seal:

Simply hammer the bearing back in with the race and seal drive, then do the same with the new oil seal.

Mock up installation

There are a few reasons that you will want to do mock installations.

First is because you want to practice torqueing the pinion nut. During final installations, the pinion nut torque sets the bearing pre-load and crushes the crush collar, but the problem is that when you crush the crush collar, you cannot back off the pinion nut to lessen bearing preload, should you over step the required measurement, because then you have over-crushed the crush collar. Therefore, I recommend installing the pinion nut and checking bearing preload once or twice as practice before you place the crush collar and make your final installations.

Second, the wear pattern is determined by the depth of the pinion head, which is set by placing a certain sized shim between the back side of the pinion head and the inner pinion bearing. But, the inner pinion bearing needs to be pressed on using an incredible amount of force, and if you go through the process of pressing on that bearing only to check the wear pattern and find that you need a different shim thickness then you are going to really frustrate yourself. To avoid this frustration, shave out the inner diameter of the old pinion bearing using either a dremmel or a file so that the bearing can be easily slipped on and off of the pinion. So on with instructions.

I've been throwing around the term bearing preload a lot, so I guess now would be a good time for me to explain it if I haven't already. Bearing preload is simply the amount of torque that it takes to turn the pinion gear. You measure this by turning the pinion with a beam or dial style in-lb torque wrench and reading the output on the wrench.

1. Shave out the inner diameter of the old inner pinion bearing so that it can be slipped on and off by hand. be sure you don't take off any of the thickness of the bearing, because that would effect your pinion depth, and then you're working with two variables, which is a mess.

you can see the scratched look on the inner walls of the bearing in the picture above.

2. Assemble the new pinion using the shim thickness that you calculated earlier (with the thickness of the old pinion head and shim) and the old, bored out inner pinion bearing. Lubricate the inner bearing and drop the assembly into the housing. Install the pinion flange and the pinion nut hand tight.

3. Now is where you can practice installing the pinion and pinion nut. You will not be able to use air tools when crushing the crush collar, so there's no point in doing it now. Just practice using your breaker bar and metal pipe. Install the pinion nut as shown in this video:

**Note: Because you are doing a mock-up installation without the crush collar, it will not take that huge amount of force shown to reach the required bearing preload**

Ford specifies 10-14in-lbs of preload if you are reusing the old bearings, and 20-28in-lbs of preload for new bearings

Use the in-lb torque wrench to measure bearing preload as shown above. Whenever I checked the bearing preload, I removed the metal pipe from the pinion flange because it would have made a significant difference in how much force it took to turn the pinion. It was somewhat of a pain to remove the bolts every time I wanted to check preload, but air tools made that less of a problem. The reason that it made such a significant difference is because of the length and weight of the pipe. Inertia would be the technical explanation, I think, but I'm not a doctor.

4. once the bearing preload is set, you can start setting the backlash.

This would probably be a good time to define backlash. Backlash is the measurement of how much space there is between teeth of the pinion and the teeth of the ring gear. When the ring and pinion are meshed together, there is still some play left in the mesh. You can see this by holding the pinion in one place and wiggling the ring gear back and forth. You will hear the teeth click together. In other words, only one side of the teeth are contacting at any one time, either the drive side, or the coasting side and say for example the drive side of the teeth is in contact, then the space between the coast side of the ring and pinion teeth is the backlash space. Backlash is probably the most important measurement in this whole install, because if the teeth are to tightly meshed, then they could heat up, expand, and seize while you are driving, if they are too loosely meshed, then you run the risk of breaking the teeth. So yeah, mildly important.

the backlash is determined by how far right and left the carrier sits in relationship to the pinion head. The closer that it sits to the pinion, the tighter the teeth mesh, the tighter the backlash, the smaller the backlash reading. Before we can start adjusting backlash, first you have to put the carrier in the housing. you want to start by gathering the new carrier bearings that came with the install kit (the carrier shims will have a different inner diameter than the ones that came from the factory so just find the ones with the same outer diameter) and coming up with a group of shims that is equal in total to the total shim thickness that you measured before. So in my case, the factory shims added to a total thickness of .539", therefore, I collected shims that were in total .539" thick or there about. For me, this was all of the shims in the install kit. Divide the shims up into two equal groups. Place the groups on the outside of the carrier bearing bores (I placed the thickest shims in the group on the inside so that as I was dropping the carrier in, I didn't run the risk of crushing or bending one of the very thin shims). Then, cover the carrier bearings with the races, and place the carrier into the bearing bores on the inside of the stacks of shims

Now it is time to measure the backlash. You need your dial indicator with the magnetic base for this. I could explain to you exactly how to set it up and run the test in words, but I'm thinking that would be a bit tedious so I'll briefly describe it and show pictures and a video.

1. First you have to set up the magnetic base of the dial indicator on the lip of the housing as shown below

2. The following video shows how to measure the backlash, but it isn't for the 8.8 differential in our mustangs, so don't follow the procedure for adjustment or the recommended specs for backlash, only notice how the dial indicator is set up and how he wiggles the ring gear to get a reading.

3. Ford recommends a backlash of between 0.008" and 0.012" of backlash for the 8.8 rear end, so if you are not within that range, you are going to need to make adjustments (I would be willing to be that everyone will need to make adjustments).

4. to adjust the backlash in the 8.8 rear end, you have to swap shims left and right to make the carrier sit further left and further right. Yes, this does mean that you need to lift the carrier out, swap shims side to side, and put the carrier back in. Be careful lifting the carrier out because the races and shims can fall into the bottom of the housing and get mixed up meaning you have to re-do your previous backlash measurement, so go slowly and do it right. To increase the backlash reading, you need to move the ring away from the pinion, which in the mustang is moving the ring towards the driver's side of the axle. Obviously it's the opposite to decrease the backlash. It takes mental math, patience, and practices to get the backlash within spec, so don't get frustrated. Remember that this is the most important measurement.

5. After swapping shims and re-installing the carrier, take a new backlash reading, and repeat the process until the proper backlash is achieved.

5. "Finally!" you might be saying, but not so fast, because you still need to check the wear pattern before you declare everything set for final installations. To check the wear pattern, even though you don't need to for setting the backlash, I think it's a good idea to have the carrier bearing end caps in place since you will be turning the gears.

To check the wear pattern, use the gear marking compound that came with your install kit, and brush a VERY SMALL AMOUNT of compound onto 4-5 ring gear teeth in 2 places on the ring gear. You really need very little marking compound. I realized that I used WAY too much after I had finished. After applying the compound, turn the ring and pinion past each other a couple of times in both directions until the pattern becomes visible.

What you want to accomplish isn't seeing how excess marking compound gets deposited on other teeth, but how the thin, almost dry layer of marking compound gets worn away by the gear contact. Look at the video below to get an idea what you are looking for in checking wear pattern and how much compound to use
you want to evaluate the dark spots among the yellow (or whatever color compound).

To figure out what the wear pattern that you have just established actually means, look at this website under the "checking the pattern" section

If you find that the wear pattern isn't correct and the pinion depth needs to be adjusted (which I did... twice), you need to pull out the carrier, pull out the pinion, remove the inner pinion bearing (that's why it's a good idea to have the old one bored out for easy removal), swap for a different shim depending on what you determined from your wear pattern, re-install the pinion, re-install the carrier, reset the backlash because it will have changed with the new pinion depth, then redo the wear pattern test. I know that that sounds like a colossal PITA but you get pretty efficient at it after the first time, and plus, it's really important to get it right.

Just remember **the backlash needs to be set correctly before determining the wear pattern**

Last edited by cstich08; 12-24-2010 at 03:08 PM.
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Old 12-23-2010, 02:03 AM   #4
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Final Installations!

You're almost there.

After you have determined that you have the correct wear pattern and the correct backlash, you can begin the final installations, which starts, ironically, with disassembly because you have to now remove the carrier and the pinion in order to press the new inner pinion bearing onto the pinion and install the pinion with the crush collar.

1. Place the pinion shim you have determined to be correct onto the pinion, then place the inner pinion bearing over the pinion gear. The bearing needs to be pressed into place. I guess it would be easiest to use a hydraulic press, but here's how I did it without one:

Place the bearing separator backwards over the bearing and set up the 2 jaw puller to pull the bearing towards the pinion head.

Don't set the bearing separator too tightly. Set it just tightly enough to sit over the inner bearing race, but not so that it drags down the shaft of the pinion gear, if that makes sense.

In this picture the bearing is already fully seated, and you can see, based on the fact that the bearing separator is bowed, that it takes a ton of pressure to get the bearing to seat.

I hit the jaw puller with an impact wrench while my dad held the bearing separator with work gloves. safety first... right.

Without an impact wrench this would have been very difficult but it is possible. To do this without one, I would find a way to very securely brace the bearing separator. Perhaps by bracing it against two large bolts bolted into a stationary work bench. Just be creative if you don't have air tools and on top of that be patient, and strong. If all else fails, simply take the gear, shim, and bearing to a shop and have them press it on.

when the bearing is fully seated, it should look like the picture that I have above.

2. slide the crush collar over the shaft of the pinion gear. There really isn't anything more to it than that.

3. Lubricate the pinion bearings well before installing the pinion because it will make a huge difference on the bearing preload measureNow slide the pinion gear into place in the housing, slide the pinion yoke onto the splines, and hand tighten the pinion nut. This is the step where it becomes CRUTIAL to not over tighten the pinion nut because you are crushing the crush collar. Follow the instructions on the video posted twice above (once in the parts section and again under #3 in mockup installation). Use a long pipe because it makes crushing the sleeve much easier. Make small turns once the sloppiness of the pinion is completely taken up. Turn the nut 1/8 of a turn, then check the preload again, because once you take up the sloppiness, the preload increases very quickly. Also, I would recommend removing whatever you have attached to the pinion yoke before you check the bearing preload. It may be tie consuming, but you may as well do this right the first time. Just be sure not to over tighten the pinion nut because you CANNOT loosen it! If you do over tighten it, then you need to get a new crush collar and try again.

Congratulations, the bearing preload is set and you're almost there.

4. Lubricate the carrier bearings and re-install the carrier with the shims that you determined gave the proper backlash.

5. Install the bearing caps on the same sides from which they were removed during disassembly. Torque the carrier bearing caps to 85ft-lbs.

6. Slide the axles into place and re-install the C-clips. push the axles as far into the axle tubes as possible in order to install the C-clips. **If you have installed the pinion shaft, you will need to remove it in order to get the axles far enough in to install the C-clips.

7. slide the pinion shaft into place. Make sure that the threads for the pinion shaft retaining bolt line up with the opening in the carrier

8. install the pinion shaft retaining bolt. I wasn't worried about torqueing this bolt I just made sure that it was sufficiently snug.

9. Re-install the differential housing cover with the new gasket provided in the install kit. I added instant gasket aka just a sealant in addition to the gasket provided. I don't know if it is entirely necessary, but I don't think it can hurt. No torque specs were given for the housing cover bolts, the service manual just says "tighten the bolts securely"

10. remove the differential fluid filler plug and add 4 oz of friction modifier XL-3, and 4.25pts of SAE75W-140 synthetic rear axle lubricant. then re-install the filler plug.

Axle re-installation

If you need, look at the pictures in the axle removal, because installation is exactly the opposite.

getting the axle back up in the car was somewhat frustrating, but I still maintain that removing it is the better option. The difficult part about putting it back in was getting it lined up and balanced while trying to install the upper control arm. I had both mom and dad helping me with this part. mom was operating the jack under the differential and dad was balancing the axle both side to side and forwards/backwards. While lining up the upper control arm bolt, you also have to make sure that the drive shaft and pinion flange mate properly. I found that it wasn't possible to attach the upper control arm then insert the DS into the flange; it had to be done at the same time.

1. place the jack under the differential housing and lift the axle into place with one person manning the jack and another balancing the axle. mate the drive shaft and the pinion flange as the axle is lifted into place.

2. attach the upper control arm to the differential housing. torque to 129ft-lbs. (I couldn't get a torque wrench up there so I hit it with an impact wrench and called it sufficient)

3. Place the springs in their perches and attach the shocks to the axles. torque to 85 ft-lbs.

4. install the 6 bolts holding the drive shaft to the pinion flange. torque to 76ft-lbs

5. install the axle end of the panhard bar. torque to 129ft-lbs. (it may take some hammering to get the bushing into the mount)

6. install the Lower control arms. torque to 129ft-lbs

7. install the sway bar axle brackets. Torque to 52ft-lbs

8. place the brake rotors over the wheel studs

9. install the caliper mounting brackets. torque the bolts to 76ft-lbs

10. place the brake pads back into the mounting bracket. Make sure that the spring clips are in place on the mounting bracket.

10. place the brake pads back into the mounting bracket. Make sure that the spring clips are in place on the mounting bracket.

11. place the caliper over the pads. for those who have changed pads before, you know that this step can be a royal PITA. it seems like no matter what you do, the calipers never want to go back over the pads. If the caliper won't fit over the pads, compress the cylinder with a large c-clamp and rotate the c-clamp clockwise. if you look at the caliper, you will see that there are two V-shaped depressions on the face of the piston. These V's need to be oriented vertically. if you drew a line between them the line would be extending out of the gap in the top of the caliper (the part that hooks over the top of the rotor). I don't really know how else to explain it. for detailed explanation of brake rotor and pad installation look at this link:

12. bolt the caliper to the caliper mounting bracket. torque the bolts to 24ft-lbs.

13. reconnect the ABS sensor wire and zip-tie the wire how it was when you disconnected it.

14. put the wheels back on.

congratulations, you just finished the install! I had a tune from brenspeed that adjusted the speedo to give the proper readout, but I hear that for manuals, there is a way to adjust the speedo without a retune. someone else will have to help me out with that write up though.

go enjoy your new gears! don't be surprised if you hear some noises at first. the friction discs of the traction loc assembly especially love to continue to make noise while turning, but I promise it will go away once they wear in a little bit.

Some people will say that break in periods are BS, but I really don't see what they can hurt. Sure, it takes a little self control. Yes, I know you wanna punch it and abuse it cause, hey, after all you just got new gears, but I would definately recommend giving it break in. If nothing else you should do the following right after the install. The first few drives, only drive for 15-20 minutes, enough to drive around for a while at full temperature, then stop and let the diff completely cool before driving agian. Break in really could make a difference in the amount of whine you experience long term, so just practice a little self control. If you are feeling particularly kind, it's not a bad idea to give the gears 500 miles as a break in period. After 500 miles you have free reign. I haven't dont this yet even after 3k miles, but changing the fluid probably would be a good idea also after 500 or so miles (I guess theoretically there could be microscopic metal filings or something floating around in the fluid, but again, I'm not a doctor so I don't know). Like I said, I haven't changed the fluid and I haven't had any problems. I want to, i've just been too lazy I guess.

TO REINFORCE, PLEASE TELL ME IF I HAVE MISSED SOMETHING PLEASE TELL ME. This was a long write up and I will not be offended if someone corrects me for any reason. If you have any further questions, please ask either in this thread or through a PM. If you are in the DFW area and would like my help, I'm more than willing to help however I can.

Last edited by cstich08; 12-24-2010 at 11:02 PM.
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Old 12-23-2010, 07:42 AM   #5
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Wish I was that mechanically inclined or bright @ 17. Great write-up/job.

With something like this though, Iīll stick to paying a dude. I like knowing how and why anyhow so I still read it, so, good deal.

Cool and kinda sad that a late 30īs short is probably the best explanation as to why and how this actually functions.
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Old 12-23-2010, 08:38 AM   #6
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wow nice write up
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Old 12-23-2010, 09:21 AM   #7
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Outstanding DIY guide.
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Old 12-23-2010, 08:01 PM   #8
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Excellent write up. Maybe i missed it, but what did you end up setting the pinion to ring gear backlash at? When i installed my 4.30s , i set it at .007" with good results. They are Motive gears in FRPP packaging and are to be set between .007 and .010.
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Old 12-24-2010, 11:54 AM   #9
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Damn son, your 17 and put a tutorial like that together? Outstanding job!
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Old 12-24-2010, 03:06 PM   #10
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Originally Posted by brunobluto View Post
Excellent write up. Maybe i missed it, but what did you end up setting the pinion to ring gear backlash at? When i installed my 4.30s , i set it at .007" with good results. They are Motive gears in FRPP packaging and are to be set between .007 and .010.
I was wrong on the suggested backlash. Looking at the FRPP website, they say backlash is to be between .008" and .012". I'm not sure about your gearset but I'm sure that your fine. The motive gears may be different in terms of backlash spec, but I'm saying that from a completely uninformed perspective and to be honest it doesn't really even make any sense why that would be true.

My backlash ended up at 0.011" which is in spec but it is on the loose side when I look at Ford's site. But it's worked out for me so far. As a bit of a story when I was taking everything apart, I couldn't even get a backlash reading from the factory setup because there was absolutely no pinion bearing preload so if I wiggled the ring gear at all, the pinion turned, so backlash wasn't even measurable. I don't know why I brought it up, but I thought it was interesting. If I had to guess I would say that the backlash was way too loose from the factory.

If someone knows for sure than say so, but I would think that the tighter the backlash, the more likely you are to have whine. does that seem to make sense to anyone else? Brunobluto, did you have an increase in whine after you did your install? Because I have a little bit louder coast, but the drive side is silent. I ask only to see if backlash makes a difference in whine.
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