Noise from rear Help!

**02bluez28** · 11-05-2007, 07:29 PM

The noise is like a clacking from the rear only heard at slow speeds when im not under power and when im turning... I know about the 10 bolt rears in f-bodies goin out, but Ive only got 40,000 miles on her with a few bolt ons...

is it possible it could something other then a shot rear end? if so what to check?

can I just replace the torsen if thats the problem?

**djvaly** · 11-05-2007, 07:46 PM

is the diff leaking? any rearend fluid spots left on the ground after you leave the car parked for hours?

**02bluez28** · 11-05-2007, 07:48 PM

Originally Posted by djvaly

is the diff leaking? any rearend fluid spots left on the ground after you leave the car parked for hours?

Nope, fluid is good level too

**djvaly** · 11-05-2007, 07:51 PM

maybe gears grinding, the fact that no leaks means the rearend/diff seals is good. I don't think your 10 bolt is shot yet.

**02bluez28** · 11-05-2007, 07:57 PM

it sounds like what is described in the stickies about a bad mechanical torsen...

**Firebirdjones** · 11-06-2007, 03:48 AM

I read your description that said clacking and turning in the same sentence and the first thing that came to my mind is that crappy torsen differential.
They make noises just as you describe when they start getting a little loose. My guess would be it's probably on borrowed time.

It's hard to have a good look at it without plopping it up on a work bench. If you have to take it that far down then my suggestion would be to get rid of it and go with a new Eaton clutch style unit. Thats what I use for most customers in all the GM 10 and 12 bolt applications.

Stay away from the Auburn units,,,,they are cone style that rely on the side of the case for preload on the coans, kinda weak and not what I call rebuildable. They are just a cheap alternative. Auburn has since offered a rebuild service for these units,,,,but it's a bandaid in my opinion. Once the case wears, you have no preload on the coans. They are re-machining the case and reinstalling cones,,,but how they get the proper preload on cones after machining a case even bigger is beyond me unless they are doing some welding. I just prefer to stay away from them as they don't seem to have a long street life and their lack of easy servicability is a big turn off for me. You get what you pay for.

Those torsens are a metal to metal style of unit with gears and plates that mesh together,,,,and in my opinion they create WAY TOO MANY metal fragments floating around. Because of this I feel regular fluid changes every 10-20,000 miles are a must with this type of differential. All that crap floating around is very hard on bearings and ring and pinions, causing premature wear and tear on an otherwise new rearend.
I even pulled my torsen out of my own car before any problems accured with only 50,000 miles on it,,,just for this reason, and installed an Eaton unit.

I prefer the Eaton units, with clutches. Completely rebuildable, with adjustability on the preload, easy to service with all parts available over the counter piece by piece if you need to. A complete rebuild kit for the unit with clutches, shims, springs, etc....only runs about $100. Been used in all the factory GM muscle cars since the early 60's and is a proven unit. The pro series has a much beefier case and heat treated spider gears, better friction clutch packs with more preload etc.....a very good unit. They don't make tons of metal like the torsens do.

**02bluez28** · 11-06-2007, 05:10 AM

If I buy a Eaton posi unit, can I install myself? can I use the stock gears or am I gonna have to replace them to? anything else Ill need? thanks for the help!

**Firebirdjones** · 11-06-2007, 10:22 AM

With proper tools,,,yes you can install them yourself. Your ring gear will bolt directly to the Eaton unit as long as you purchase the same series carrier that you currently have with the proper spline count. All 7.5 inch 10 bolts went to 28 spline after 1988.

With only a carrier change,,,sometimes you get lucky and you can re-use the original cast iron shims and your back lash may be correct,,since you are reusing your original ring gear and the pinion does not have to come out. If not then a shim kit will be needed. Some people rely only on marking compound and look for a certain pattern on the gear both on the coast side and power side. This can work if you know what you are doing, but I prefer the dial indicator method,,,,if the backlash and pinion depth are set properly then the gear pattern will be correct,,,,sometimes I run some compound on a gear set just as a second measure for giggles.

A dial indicator with a magnetic base will help here. It will be needed to check and set proper back lash. If too much or too little,,,,then shims will be needed to move the carrier from side to side until proper lash is obtained. Keeping in mind that setting backlash here is not the only critical adjustment,,,,you also have to keep proper preload on the side bearings as well that are on the carrier. I would have to check the book but I believe .004 preload is in the ball park with about .006-.009 backlash. From there if you wish you can apply some gear marking compound and see where it is at. A good idea is to check backlash with your dial indicator before the old carrier is removed so you have something to go by, and it may tell you a few things. Excessive backlash can cause a clunking sound on accel/decel, and can also cause gear whine.

Speaking of the side bearings,,,,if you have a press with the proper bearing removal tool,,,,you can remove your old side bearings from the original carrier without damage,,,,and reuse them if they look good. Close inspection of the bearing surface here and look for pitting, use your own judgement here,,,but if I see anything at all,,,they get tossed,,,they don't cost much and isn't worth the hassle. If so,,,,new carrier bearings will be needed and pressed on. New gasket and gear oil.