4.10 Gear Issue Please Help

Fury50 · May 14, 2012

I have a 2012 GT. I had the ford racing gears put in my car saturday. The guy doing the install has done literally thousands of rears in mustangs. Hes never had a problem like the one with mine. The gear whine is so so bad its rediculous. It sounds like a fire truck siren and is just as loud. Hes redone the gears 4 times now. I bought from american muscle with the motive install kit. He said hes seen ford gears have issues on rare occassion but nothing like this. any ideas??

Svtpilot · May 14, 2012

Did he replace the pinion bearing with the gears? If not, I would look at that first. In the description section for Ford Racing gears on the American Muscle Website is the following note:

Attention 2010 and newer Mustang Owners. Starting in 2010 Ford changed the inner rear gear pinion bearing in all 8.8" equipped Mustangs. Because of this you will require a new 8.8" rear gear pinion bearing (Ford part# 9L3Z-4630-A) ...

Assuming that the above is not the problem:
Is the noise all the time or when coasting with your foot of the gas? If is when coasting it is bad pinion bearing. Generally a steady gear whine is due to faulty installation such as incorrectly adjusting the back lash or defective/damaged gears. When you say that he has redone the gears four times do you mean that he reinstalled the same ring and pinion 4 times or that he installed 4 different gear sets? If he installed different gear sets then you can pretty much eliminate defective parts. If he is reinstalling the same set then it is possible that the 1st installation is done incorrectly and they were damaged as a result. There are also the ridiculously stupid possibilities that also have to be eliminated, such as forgetting to refill the diff, or some how reinstalling the panhard rod so that is touching the diff cover (if that is even possible)
Well good luck and let us know how it turns out.

Fury50 · May 14, 2012

Svtpilot said:
Did he replace the pinion bearing with the gears? If not, I would look at that first. In the description section for Ford Racing gears on the American Muscle Website is the following note:

Assuming that the above is not the problem:
Is the noise all the time or when coasting with your foot of the gas? If is when coasting it is bad pinion bearing. Generally a steady gear whine is due to faulty installation such as incorrectly adjusting the back lash or defective/damaged gears. When you say that he has redone the gears four times do you mean that he reinstalled the same ring and pinion 4 times or that he installed 4 different gear sets? If he installed different gear sets then you can pretty much eliminate defective parts. If he is reinstalling the same set then it is possible that the 1st installation is done incorrectly and they were damaged as a result. There are also the ridiculously stupid possibilities that also have to be eliminated, such as forgetting to refill the diff, or some how reinstalling the panhard rod so that is touching the diff cover (if that is even possible)
Well good luck and let us know how it turns out.

the pinion bearing was replaced.
the same gears were used each time
there is fluid in the differential
for the first couple minutes it was only on deceleration now its accel and decel.

I called a dealership close to me and heard something very odd. The guy told me the g410m (the gear i got from am) was disscontinued and the new gear is 420988410. He discribed to me what the sound was without me even telling him. Any ideas if that has any weight to it??

jetmech807 · May 14, 2012

Trying giving AM a call. Never read a bad thing about their customer service.

Sent from my PC36100 using Tapatalk 2

Fury50 · May 14, 2012

jetmech807 said:
Trying giving AM a call. Never read a bad thing about their customer service.

Sent from my PC36100 using Tapatalk 2

I called them earlier. They want a shop report before theyll do anything which is understandable. Funny part is the whole setup is cheaper from the dealership by $55.

SpartaPerformance · May 14, 2012

Yes the 420988410 is the New Style gears, the old gear once and while would howl like a wolf. The new gears are actually made by Ford in one of their axle plants unlike the previous gears.

Fury50 · May 15, 2012

well stopped by the shop last night and the car is still apart. i dropped off the new gears/pinion bearing/install kit and told the one guy about the gear differences. he went through the garbage and it is the 420988410. My order says g410m but whatever. Theyll be pulling the rear apart again today and well see what happens in the mean time he did 410 richmonds and motive 373 in a 11 and 12 gt. no issues. so i dunno wtf. im hoping the new stuff will go in without issue but who knows anymore. im sure you can tell im aggrivated over all of the bs . this is my 9th mustang and every 1 has had aftermarket gears. This is the 1st time ive had an issue.

Fury50 · May 17, 2012

ok so heres what happened. My order from A.M. had the wrong pinion berring. It was hard to tell by just looking but when I bought the right berring from Ford it fit 100 times better. So with it not fitting in scored the teeth on the pinion pretty bad. (i didnt do any more then just put around for a few minutes to find out when the grinding occured) So basically I bought 4.10 gears and install kit 2 times in a week.

Anyway now its perfect.

Bojingles · May 17, 2012

Good info. Did AM help you any with that?

Fury50 · May 17, 2012

Bojingles said:
Good info. Did AM help you any with that?

not yet but we'll see when i call them.

Svtpilot · May 17, 2012

Pinion bearing? Wish I thought of that. Glad it worked out for you, the way it was headed I thought it would take forever to figure it out. So now that is is fixed how do you like the 4.10s?
Oh and thanks posting the solution. It annoys the crap out of me when guys post question about problems but don't let us know how it was resolved,

Fury50 · May 18, 2012

the 4.10s are really nice BUT if you have manual and you plan on takin off from lights or at the track you better know how to shift FAST. When I take off im in 4th gear before I even realize it. Very fun to drive. I upgraded to 285 nt555 nittos. That was a must. the stock tire would spin probably through the first 3 gears.

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