Rear end woes
Thread Starter
10 Second Club
Joined: Dec 2002
Posts: 315
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From: Baton Rouge,LA
Rear end woes Ok guys heres the deal on my rear,i need some opinions.
Last year (Aug to be exact)my stock rearend had the carrier bearings go out.i decided it was time to take advantage and rebuild with 3.73 gears and all new bearings and seals.Everything was fine,i picked up .2-.3 and 1-2 mph in the 1/4.In Jan I installed my Midwest convertor i was very pleased with the setup.In may the gears started whining a bit so i brought it back to the place that installed them and he said the backlash had moved to about 20 thousanths,we came to the conclusion that the gears werent cut exact from the factory(US Gear)and they wore in.He reset the rear and it was back to normal.Less than a month later the bearings went out again,the races and the rollers were flaking apart .so he replaced the bearings again and reset the rear,he said the wear pattern looked good.four days later the rear all of a sudden started sounding like a siren(I couldnt here my exhaust over the whine) So I dropped it back off and he found the backlash at 30 thousanths,he reset it again and said that it wore a grove in it and the noise wont come out He said that the rear is set up with a 2 series carrier with 3 series gears,is this true?He wants to put in a eaton posi unit with a new set of gears.Im kinda leery to do this,should I?Im contemplating the idea of going with the Ford 8.8 setup since I cant afford the 9" or 12 bolt.
I havent been to the track since about March so the rear hasent seen any real abuse ,plus its an A4 so it dosent see as much shock as the M6.Ive been told that the whining will not hurt anything to drive,it will just be loud,im going to take a trip to florida this coming week and was planning on driving the car,should I?
any opinions will be much appreciated.
Last year (Aug to be exact)my stock rearend had the carrier bearings go out.i decided it was time to take advantage and rebuild with 3.73 gears and all new bearings and seals.Everything was fine,i picked up .2-.3 and 1-2 mph in the 1/4.In Jan I installed my Midwest convertor i was very pleased with the setup.In may the gears started whining a bit so i brought it back to the place that installed them and he said the backlash had moved to about 20 thousanths,we came to the conclusion that the gears werent cut exact from the factory(US Gear)and they wore in.He reset the rear and it was back to normal.Less than a month later the bearings went out again,the races and the rollers were flaking apart .so he replaced the bearings again and reset the rear,he said the wear pattern looked good.four days later the rear all of a sudden started sounding like a siren(I couldnt here my exhaust over the whine) So I dropped it back off and he found the backlash at 30 thousanths,he reset it again and said that it wore a grove in it and the noise wont come out He said that the rear is set up with a 2 series carrier with 3 series gears,is this true?He wants to put in a eaton posi unit with a new set of gears.Im kinda leery to do this,should I?Im contemplating the idea of going with the Ford 8.8 setup since I cant afford the 9" or 12 bolt.
I havent been to the track since about March so the rear hasent seen any real abuse ,plus its an A4 so it dosent see as much shock as the M6.Ive been told that the whining will not hurt anything to drive,it will just be loud,im going to take a trip to florida this coming week and was planning on driving the car,should I?
any opinions will be much appreciated.
Re: Rear end woes Did your carrier races get scalded or have marks on the outside of them where they sit in b/w the housing and saddles? If so you have ruined your housing. What you did was when those bearings went bad the races began to turn with the carrier bearing and this ground out your housing making the area that holds the carrier race out of round. Now if you try to put in another set of carrier bearings you're gonna get the same thing happen. Either have your housing repaired or get a new rearend. I would not drive the car if this is your situation, if your rear locks up then bye bye transmission, driveshaft, etc.
Re: Rear end woes I've had the same thing happen, I've replaced my carrier bearings twice b/c they were eatin on the inside near the bearings. The problem was with the setup of the gears. We had a perfect 10 backlash on them but the way we shimmed them was that it was soo tight it kept pushing the bearings against the races, they were not spinning just too tight. Now I re-did it again and shimmed it correctly, re-setup the gears and now it is perfect! no whine, no grinding. And when my rear-end did lock up the first time when the carrier broke it did not brake my trans or driveshaft, and it was locked up solid, however I was going a very slow speed 5 mph. Got lucky 
Re: Rear end woes You'd better check your carrier bearing housings (where they reside in the housing) to be sure they aren't out of round. Trust me, if they are out of round you're gonna keep destroying bearings and eventually the rearend and then some.
Think about it, if the compartment that the round race resides in is no longer round but now an oval shape the race has a risk of binding and if your carrier bearings inside the race bind then the race will spin with the bearings essentially honing out the saddles and the housing. It's not worth paying for numerous teardowns if you can stop it here.
For your sake, please just have the installer mic the saddles and carrier race slots in the housings to be sure they aren't out of round.
Think about it, if the compartment that the round race resides in is no longer round but now an oval shape the race has a risk of binding and if your carrier bearings inside the race bind then the race will spin with the bearings essentially honing out the saddles and the housing. It's not worth paying for numerous teardowns if you can stop it here.
For your sake, please just have the installer mic the saddles and carrier race slots in the housings to be sure they aren't out of round.
Re: Rear end woes Also, doesn't the fact that your backlash keeps changing even though you have not done any hard launches on sticky tires, etc make you go, "hmmm...". Backlash should not change if you are not doing lots of repetitive launching on sticky tires and cutting low 60' times. Backlash will change with normal driving but it shouldn't at the amount your installer is changing. Twenty thousandths of a need backlash adjustment is A LOT for little abuse.
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Thread Starter
10 Second Club
Joined: Dec 2002
Posts: 315
Likes: 0
From: Baton Rouge,LA
Re: Rear end woes Ive been thinking about going with the 8.8 but I feel that the shop that has been doing the work should make it right.Damn,the rearend should last longer than 10 mos before going 
It seems that the problems started when they reset the gears in May.
It seems that the problems started when they reset the gears in May. Re: Rear end woes If the install was done improperly it can cause your housing to be damaged. If you have access to a digital camera snap some pics of the carrier bearing races' and the smooth portion of the carrier bearing saddles and post them up.
Actually, if you see any black lines or grooves on the races and/or the saddles then the housing is pretty much toast. You'll be able to put new gears, etc in but you'll keep eating up races, bearings and eventually break the differential. If that breaks you could lock up the rearend which could lock up the driveshaft and boom, tranny is gone
The carrier bearing saddles' should have a nice cross hatch pattern similar to what you would see in a freshly honed cylinder bore.
Actually, if you see any black lines or grooves on the races and/or the saddles then the housing is pretty much toast. You'll be able to put new gears, etc in but you'll keep eating up races, bearings and eventually break the differential. If that breaks you could lock up the rearend which could lock up the driveshaft and boom, tranny is gone
The carrier bearing saddles' should have a nice cross hatch pattern similar to what you would see in a freshly honed cylinder bore.
