Marksman14

Details about what happened:

Last year I had a speed shop in Schaumburg install a 4.10 ring and pinion. From the MINUTE I got the car up to 40mph, I could tell something was wrong. I noticed a low pitched hum/vibration coming from the rear end. Now, its not terribly loud, but I notice it. I paid specific attention to the noises coming from my car prior to the install to ensure that I knew about everything going on back there.

The noise is noticable at 40 mph, and then around 60mph. Undetectable under 40, and over 65 or so. I complete the three heat cycles as per their break-in procedure, and the noise is still there. No better or worse, still the same.

I call the shop, and bring it back in. They rotate my driveshaft 180 degrees, and the noise for whatever reason seems to dampen SLIGHTLY, but it is still there. Not as bad at the lower speeds, but near 60 its still there.

They claim there is NOTHING wrong with the car or the install. However...they replaced no bearings, and used standard fluid. I have heard mixed reports on these potentially being problems, but the car went in with 11k miles on the clock. The tech explained his procedure on the pinion bearing, and that was that. Seemed reasonable at the time, but long story short, they would not open it up and take a look, since they claimed they couldn't hear the noise.

Now, I set the car up for winter, and get back in it this weekend. I'm driving it, and just happy to be in the mustang. The noise isn't that bad I'm thinking, so I take it out on the highway and give it some gas. Anyways, I'm ok with it until I get the differential heated up, and then at 60mph, the noise gets louder. Can't detect a change in the noise at 40 with it heated, but at 60 its now more noticable.

So...lets recap/specify certain details-

1- Noise detected after FRPP 4.10 install- speed shop flips driveshaft, has minimal effect
2- Speed shop claims they cannot hear the noise, tells me "sorry, nothing we can do" even after reusing all bearings and using standard gear oil.
3- Noise worsens as differential heats up
4- Noise is low pitch. Almost like a resonating vibration (IE, at certain wavelengths, the vibration is audible)
5- The noise increases in a linear fashion- As speed increases, the audible pitch increases. IE, at 60mph, it is slightly louder and higher pitched than at 40.
6- The noise occurs regardless of engine/trans activity. I can shut the motor off and put the clutch in and as long as the rear wheels are spinning, the noise is present.
7- I'm absolutely pissed and it makes driving the car a pain in my ***.


So, logic tells me that all signs point to the ring and pinion. I understand 4.10 gear sets can occasionally produce noise, but this ain't right. So, I am having the ****er completely redone.

1- Getting a FRPP 3.73 gears- is M4209F373 the right product number? I'm ordering from latemodelrestoration.com
2- I am having a different shop do the installation (no ****)
3- I am going to use an install kit similar to this one http://www.stangmods.com/8-8-Gear-In...660-m4210c.htm,
4- They are using OEM 75W140 gear oil in the install with the friction modifier- should I use royal purple?


Essentially I would like to know if I have my bases covered for the new gears. I want to make sure that my part numbers are the ones I need, I get the right install kit, and use the right fluid/additive. I want this ****er to be flawless when I am done, and that is that.

Lastly- One of the shops said that there is a minor possiblity that the differential itself may have been warped from the heat caused by the ring and pinion...and its possible that there may truly be a problem with the current install beyond "well, sometimes gears make noise". Have any of you heard of this happening, and if so, where the hell can I get a new differential for under 500 bucks?

THANKS FOR YOUR TIME GUYS, you have no idea how much help this forum has provided, I just need some reassurance from you guys that I'm on the right track.

Scott

ajaibr

Honestly, gears sometimes do make noise that have nothing to do with install. The higher the numerical gear is, the more likely it is to happen. If you want to talk about good shops in your area, message me. I'm from Streamwood. If you want me to take a listen and tell you what might be going on I'd be happy to.

Simon1

I'm on my 3rd set of gears.

First set was quiet and was replaced by Ford during the TSB with 4.10s. Very noisey from 50-75. It was free so I didn't complain.

3rd set is 3.55s with Detroit locker. Pretty quiet, some noise from 65-90 but very slight. Exhaust and turbo noise drowns it out.

I'n considering putting the stock diff back in with a new set of gears. 3.55s again. I used the gears from Yukon with the RP gear oil.

It's rare that I hear someone say they don't hear any noise after any gear install on our cars.

david01130

Is there a reason you chose 3.55s over 3.73s when I am assuming you put the turbo on? I have 3.55s and am considering 3.73s. Im blown.

157dB

If the driveshaft was removed, it should have been marked prior
to removal for proper reinstallation. This can cause all sorts of noises.

moosestang

+1, but it should vibrate the faster you go. Mine was fine until 70mph. It is critical to put the drive shaft back exactly as it came out.

I think I got really lucky with my gears, they are quiet and have been for 2 years now. Rolands automotive in Gainesville, FL is a good shop.

They should have at least replaced the inner pinion bearing. Getting it off without damaging it is difficult, i'm told. I'll try to take a pic of my old pinion bearing, they bent it up good.

I used royal purple and it likes to puke it out the vent tube. I probably over filled it some, but I'm going to try adding a vent line, instead of that little stock fitting. It never gets on the driveway, just covers the axle tube.

Did the new shop drive the car? I'd make sure it's the gears before going through all that trouble.

The stock diff is under $500, i think.

East87

Sorry to hear about your troubles, Scott. This seems to be the only surefire way to avoid problems when changing gears...get a whole new rear end.

http://www.newtakeoff.com/mustanggt8...mustanggt.aspx

Riptide

Much as I hate to say it I agree that complaints about whiny/noisy rear ends are commonplace with aftermarket gear installs in these cars. I have no idea why they are so finicky about it - but it is what it is. At this point I'm expecting the worst and hoping for the best. When I eventually get a 4.10 install done I am planning on dealing with the resulting noise as best I can - make the exhaust loud enough to help cover it up. As long as it doesn't break on me I've pretty much resigned myself to dealing with this problem.

Simon1

Because of the turbo.

If I had a regular supercharger I would have something in the 4.10 range. The 3.55's are pretty good for now. I will try and make enough passes this summer to get a feel for the launch I get. Maybe I'll got to a 3.73 but probably not.

JimsGT

Wow, thats the exact same problem on my car as well!( except for the vibration) I went from stock 3.31's (automatic here, for the record, also, stock driveshaft), to Ford Racing (FRPP) 3.73's. I went to a local shop, a one man show that is big with the 5.0/Fox body crowd, but he also does S197 work, he was a former Ford tech for years. Anyway, I had him order the FRPP gears, 3.73's,(part no. M-4209-F373 N)...I guess they're the "M" Motive gears everyone's been talking about, but try finding the "A" numbered gears! So he did the install, but he never ordered the FRPP gear installation kit (part no. M-4210-A). I never questioned him on that, whether he needed it or not, etc. or if he had one lying around. ( I'm sure he would have charged me for one if he used it, because its roughly 40 bucks.) He used 2 qts of Royal Purple "Max Gear" 75W 140, and 1 bottle of the Ford friction modifier additive. So, after it was done, I asked him about heat cycles, he said don't worry about that, just drive it , but don't "get on it" for 500 miles. So I did one better, and didn't "get on it" for 1,000 miles. I really didn't notice the noise at first, but it got gradually louder, and like you said only from 40 through 60 mph on acceleration, then it disappears, and again from 60 mph to 40 when you coast, no gas, then it disappears. Its not real loud, but its a howl, like wind as opposed to a high pitched gear whine sound. I read here some guys were filling the rear with more fluid until it was level with the fill hole, I had him do that, it took another 1/2 to 3/4 qt. of Royal Purple, but that did not work either. So he finally said its how the gears are made (cut). He said " its on the backside of the gear, they call that the backside, no big deal, its ok". I'm not totally convinced, especially since he didn't use the gear install kit. The car had 18,000 miles on it, I did it last June, now the car has 23,000 miles on it. I will take it to another shop to get a second opinion. Well, thats my lengthy story, hope it helps somewhat!

BTW : I've heard using Royal Purple ( or any other synthetic) as the way to go, I've heard never use synthetic, ever, and I've heard if you use the RP you don't have to use the friction modifier. My installer, like the majority of people, used the RP plus the friction modifier. Also, everyone says to use the FRPP A part numbered gears, as opposed to the M part number gears as they are made by Motive gear for Ford and they are allegedly noisey by nature, but try finding these A numbered gears, I've yet to see it in magazine ads, online vendors, the FRPP site, etc. Good Luck, I hope it all works out for you. I don't know jack squat about doing a gear install, but not using that gear install kit stays on my mind, I have my doubts. I dropped the car off in the morning, by noon he was done, was it too fast, who knows. (500 bucks, parts and labor)