Differential rebuild (I don't trust any local shops)

**TacitCaucasoid** · 10-31-2012, 08:44 AM

Hey everyone
I have ran into an issue with my rear end making a whirring sound. Almost like beaings are going bad. I put the car up on jacks and stuck her in 6th gear to see where the noise was coming fom exactly and I've narrowed it down to the diff. I am going to check the fluid levels in it tomorrow after work and hope for the best but...

I would like to have taken this to a pro because I don't have enough experience with rebuilding one although, i do have a best friend that is willing to help. I'd rather do it myself to learn ya know?

I've been searching all day to see if I can get a rough estimate on parts, costs and what special tools i need to complete this in a weekend if possible. If any one has some advice or a better alternative feel free to comment.

Unfortunetly I do not have the necessary found for a 12 bolt, otherwise this post would be a moot point.
Also, i checked my local yards and can't find any rear ends to match up to my 99 Formula.

**redbird555** · 10-31-2012, 09:43 AM

Originally Posted by TacitCaucasoid

Hey everyone
I have ran into an issue with my rear end making a whirring sound. Almost like beaings are going bad. I put the car up on jacks and stuck her in 6th gear to see where the noise was coming fom exactly and I've narrowed it down to the diff. I am going to check the fluid levels in it tomorrow after work and hope for the best but...

I would like to have taken this to a pro because I don't have enough experience with rebuilding one although, i do have a best friend that is willing to help. I'd rather do it myself to learn ya know?

I've been searching all day to see if I can get a rough estimate on parts, costs and what special tools i need to complete this in a weekend if possible. If any one has some advice or a better alternative feel free to comment.

Unfortunetly I do not have the necessary found for a 12 bolt, otherwise this post would be a moot point.
Also, i checked my local yards and can't find any rear ends to match up to my 99 Formula.

You cant rebuild the rear diff in these cars... You have a torsen unit in your rear end which uses worm gears inside to engage the positraction, and honestly it most likely is the bearings causing the noise. You probably need to replace the carrier bearing as well as the wheel bearing all of which can be done with a press and some time, however resetting the backlash on the rear would be ideal when this is done.

**TacitCaucasoid** · 10-31-2012, 11:22 AM

I haven't been able to find a write up on this. Is there one?
And I will reset it.
One more question about it: Is this common for birds with 109k on them?
Thanks for the help redbird555

***SMWS6TA*** · 11-01-2012, 07:56 AM

I have a spare torsen unit. It came from a donor rear end project of mine. Not sure the ring/pinon ratio count is because I forgot if it came from a A4 or M6.

If interested let me know, I'll send a pic or two. I'm not asking much just need it gone.

Also, many of us here will tell you investing in the 10 bolt is a waste of time and money, start saving for a better one. But if it's a DD and you're not planing on modding past bolt ons then I could understand rebuilding the 10 bolt.

**Knight** · 11-01-2012, 08:29 AM

Agree with Scott. You can also pick up a better carrier than the torsen unit for a replacement. It will help prolong the life of the rear a bit. At that point though, you'll be getting close to the cost of a 12 bolt or 9". Figure in shop labor for pressing bearings, if you don't have a press, and can find on willing to do it. My recommendation would be baby it, if you can save enough to replace the entire rear in a while. In the end, it really is the better choice. You may rebuild the rear, only to have it fail again shortly after. Some people have decent luck with them, the majority do not.

**TacitCaucasoid** · 11-01-2012, 09:02 AM

Right, I know the stock rear end isn't the greatest.
She is my dd so SMWS6TA I would love to take you up on that offer. I'm looking at her again this evening to confirm what's going on with it.
I do plan on swapping out a 12 bolt but that may not be until next summer.

**TacitCaucasoid** · 11-02-2012, 03:31 AM

Jacked her up about 3 feet in the air, took a pipe to listen to the internals but it was kind of hard to hear where the noise was coming from. Me and my best friend (who happens to be a fleet mechanic) put the car in neutral and rotated the tires by hand. Further listening, paired with my best friends experience showed us that it is not the diff making the noises after all, it's the axle shaft bearings.

That being said it has made this noise since i bought it so I knew I would have to do some work to the rear end. I don't know how long it has been like this so I don't know if the axle shafts are bad as well.Also the rotors are warped so i will need to replace those as well as the brakes lol.

**Hot Black Trans-Am** · 11-02-2012, 05:04 AM

Stock rear brakes warp after about 1500 miles. They suck badly.

**TacitCaucasoid** · 11-02-2012, 05:44 AM

It seems like GM was a hit and miss with quality on this car.

***SMWS6TA*** · 11-02-2012, 07:26 AM

Originally Posted by TacitCaucasoid

It seems like GM was a hit and miss with quality on this car.

It's not just GM...I can pick apart any car company.

For Rotors I'd recommend going with R1 Concepts. Quite a few members use them and I've heard nothing but good reports on them. It's currently on my to do list.

They may be a little more then a stock replacement but I'd gladly pay a little more to get a better product.

Disc Brake Rotors & Pads | R1Concepts.com

**herculesrider1** · 11-02-2012, 01:22 PM

Ready for this? I purchased a '98 TransAm WS6 M6 new from the factory, picked her up with 25 miles on it. When I reached 25,000 miles...whinning rearend....replaced under warranty. At 50,000 miles...whinning rearend again....replaced under warranty. At 75,000 miles...whinning rearend...replaced under warranty....warranty ran out at 100,000, so drove it til I flipped it at 152,000. I now own this '00 TransAm WS6 M6, bought it from a guy in Maine who had built it for racing and put a Midwest Chassis 9" with a Strange nodular S case, daytona support, 1350 series yoke, 4.10 gear, and a Truetrac diff unit and it still has a whinning noise. This is suppose to be a bulletproof rearend, and I'm still having to rebuild it after only 55,000 miles on this new rearend. This is the first car I have ever had this much trouble with a rearend....every other car I have ever owned since 1972 has not had ANY rearend trouble. Still scratching my head over this one!....But all in all, it's still worth owning it...just would be so much better to not have all this rearend trouble!!!!!

**TacitCaucasoid** · 11-02-2012, 09:11 PM

I took out the axles and the diff.
I found a lot of metal shavings on the magnet and the fluid had to have been mixed with water because it smelled like your local picknpull junkyard and was an odd color.

That being said, the only bearings that were bad was the carrier bearings. I'm replacing those and the races along with the rear rotors and brakes.

A wash n wax too lol