8.8 gear swap, hope this helps
03-06-2009, 10:34 AM
#1
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Join Date: May 2007
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Posts: 38
8.8 gear swap, hope this helps
I'm always asking for help and advice in the forum, so I thought I'd finally give back a little. I just completed round 2 of a rear end set up and figured I'd pass along some info to help any other shade tree mechanics attempting this project. First things first, I used the following link, and years with hands on a wrench for the basic how to's. I mainly just want to cover some issues I had and hope it helps. Just to note. Round 2 has less than 150 miles so far, so it still may have issues, but so far so good.
CarTech, Inc.: Browsing Ford 8.8 Inch Differential Gear Swap
NOTE: I did not find this job hard, but more of an art than just turning wrenches, which led to long hrs of frustration. I've heard that most shops will do this for a couple hundred bucks, and unless you are just really curious, or have a strong desire to learn a new skill, or just have pride in doing your own stuff..... PAY SOMEONE!!!!!!! I did it for all of the above reasons, and will probably never do it again... lol, the "tuition" at this school was more than I wanted to pay. If you still want to do it yourself, I respect that, so read on, maybe it will help.
Tools you'll need and may not have to do this job are: A press, as the pinion bearing must be pressed on. A torque wrench with a needle (not a click style) that can measure small increments (10-30 IN-lbs), dial indicator, bearing/seal installation tools, axle bearing puller and slide hammer and a 3 and 2 jaw puller some of which you can probably rent at the local parts store.
Next, tricks I picked up that may help. The problems I had with round one were a shallow pinion depth and not enough preload on the the bearings. The first problem can be solved one of two ways. The easiest is a lucky guess, but I don't recommend this, b/c if you are wrong, you have to press the bearing back off (risking damage) to change shims. The next is to either buy an extra bearing (less than $20) or press the old bearing off of the old pinion. To do this you will need a bearing knife to get under the bearing to press it off of the pinion. Take this bearing and mill, grind, or file the inside SLIGHTLY, so that it will just barely slide on and off of the pinion. I also recommend taking steel wool or a scotch bright to the new pinion where the bearing sits, to get all the rough off of it. On that note...... you'll want to wire wheel the pinion flange teeth, on the pinion, and add some grease when installing the pinion flange, and test fit it on the bench, until it reaches the bottom of the teeth. If not, it may bind during install and prevent proper preload. With this "mock up bearing" you can install the pinion with both bearings and the diff assemble to test gear mesh pattern. Some where on the internet, I can't find it now, is an excellent description of proper gear mesh, but hear it is in a nut shell. You want the pattern in the middle of the ring gear teeth. If the pattern is toward the inside of the ring gear, you need less shim. If its on the outside, you need more shim. Also, the backlash here needs to be close, but not perfect at this time. You do not need a crush sleeve or pinion seal at this time. Just make sure the pinion flange is seated so that there is NO slack in the bearings or pinion.
Now for problem two, improper preload. Once you have the proper shim for the pinion depth, you can press on the good pinion bearing and install the pinion with the front bearing and pinion seal, and crush sleeve. The pinion flange should go on with some resistance, but not too much, then you'll hit the crush sleeve. It will be very stiff at first (in the area of 150 ft/lbs) but will then collapse and the tension will ease up some. This is where you use that torque wrench to start measuring drag, b/c it will tighten up quickly. NOTE: the should be NO slack in the pinion flange assembly. The info I have says about 20 inch/lbs of rotational drag. I never could get my hands on a proper torque wrench, so I used a 12 inch bar, and, believe it or not, a fish weight scale to measure the amount of drag. It should be about 1.6 ft/lbs. HOWEVER, I do NOT recommend this, b/c I'm not sure of its accuracy and I may have overloaded mine just a touch... time will tell. Just one of those things you come up with at 11 pm and improper tools. One other note. the crush sleeve that came with the second set of gears was very thick walled compared to the one that came in the rear end rebuild kit. Watch out for this b/c that heavy one is a son of a gun to get seated.
I found backlash fairly easy to adjust, and actually was fortunate to be able to use factory shims to obtain .013. this may be slightly loose, as the info I have says .008-.012, but that's pretty close and I've HEARD that under .015 is good. Also, if using FRPP parts, they have a tech line 1-800-367-3788. So, good luck and hope this helps!!
CarTech, Inc.: Browsing Ford 8.8 Inch Differential Gear Swap
NOTE: I did not find this job hard, but more of an art than just turning wrenches, which led to long hrs of frustration. I've heard that most shops will do this for a couple hundred bucks, and unless you are just really curious, or have a strong desire to learn a new skill, or just have pride in doing your own stuff..... PAY SOMEONE!!!!!!! I did it for all of the above reasons, and will probably never do it again... lol, the "tuition" at this school was more than I wanted to pay. If you still want to do it yourself, I respect that, so read on, maybe it will help.
Tools you'll need and may not have to do this job are: A press, as the pinion bearing must be pressed on. A torque wrench with a needle (not a click style) that can measure small increments (10-30 IN-lbs), dial indicator, bearing/seal installation tools, axle bearing puller and slide hammer and a 3 and 2 jaw puller some of which you can probably rent at the local parts store.
Next, tricks I picked up that may help. The problems I had with round one were a shallow pinion depth and not enough preload on the the bearings. The first problem can be solved one of two ways. The easiest is a lucky guess, but I don't recommend this, b/c if you are wrong, you have to press the bearing back off (risking damage) to change shims. The next is to either buy an extra bearing (less than $20) or press the old bearing off of the old pinion. To do this you will need a bearing knife to get under the bearing to press it off of the pinion. Take this bearing and mill, grind, or file the inside SLIGHTLY, so that it will just barely slide on and off of the pinion. I also recommend taking steel wool or a scotch bright to the new pinion where the bearing sits, to get all the rough off of it. On that note...... you'll want to wire wheel the pinion flange teeth, on the pinion, and add some grease when installing the pinion flange, and test fit it on the bench, until it reaches the bottom of the teeth. If not, it may bind during install and prevent proper preload. With this "mock up bearing" you can install the pinion with both bearings and the diff assemble to test gear mesh pattern. Some where on the internet, I can't find it now, is an excellent description of proper gear mesh, but hear it is in a nut shell. You want the pattern in the middle of the ring gear teeth. If the pattern is toward the inside of the ring gear, you need less shim. If its on the outside, you need more shim. Also, the backlash here needs to be close, but not perfect at this time. You do not need a crush sleeve or pinion seal at this time. Just make sure the pinion flange is seated so that there is NO slack in the bearings or pinion.
Now for problem two, improper preload. Once you have the proper shim for the pinion depth, you can press on the good pinion bearing and install the pinion with the front bearing and pinion seal, and crush sleeve. The pinion flange should go on with some resistance, but not too much, then you'll hit the crush sleeve. It will be very stiff at first (in the area of 150 ft/lbs) but will then collapse and the tension will ease up some. This is where you use that torque wrench to start measuring drag, b/c it will tighten up quickly. NOTE: the should be NO slack in the pinion flange assembly. The info I have says about 20 inch/lbs of rotational drag. I never could get my hands on a proper torque wrench, so I used a 12 inch bar, and, believe it or not, a fish weight scale to measure the amount of drag. It should be about 1.6 ft/lbs. HOWEVER, I do NOT recommend this, b/c I'm not sure of its accuracy and I may have overloaded mine just a touch... time will tell. Just one of those things you come up with at 11 pm and improper tools. One other note. the crush sleeve that came with the second set of gears was very thick walled compared to the one that came in the rear end rebuild kit. Watch out for this b/c that heavy one is a son of a gun to get seated.
I found backlash fairly easy to adjust, and actually was fortunate to be able to use factory shims to obtain .013. this may be slightly loose, as the info I have says .008-.012, but that's pretty close and I've HEARD that under .015 is good. Also, if using FRPP parts, they have a tech line 1-800-367-3788. So, good luck and hope this helps!!
07-06-2012, 02:01 AM
#6
Thread Starter
Join Date: May 2007
Location:
Posts: 38
Glad to know a 3 yr old post is still helpful. I have also since learned that the diff carrier bearing caps are machine matched to the diff. Make sure they stay in the same orientation (left, right, up, down), or it may pinch the bearings, and you'll be in again 
Experience is not always the funnest way to learn.
Experience is not always the funnest way to learn.
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