Anyone good with Eaton positraction differentials?

Hello guys, long story short I bought a 02 Camaro SS in 2013, I've been using it for auto x and just cruising it on weekends since then. So ever since I bought it the rear end clunked / snapped around corners but lately its getting worse. It rattles the drive shaft and sound horrible since its a six speed car. Last weekend I finally got around to pulling the rear apart. Its a Moser 12 bolt with an Eaton posi. Only about 10k on the rear.  I'm thinking the clutches are either shot or getting dry from sitting and are causing the sound when they lock and unlock. (The car sits for months at a time)

Here are some pictures of the clutches I took out tonight. I know they look worn but I don't think they look that bad? I really don't have anything to compare to since its my first experience with a posi unit.  Does anyone know if these are the carbon faced clutches? They do look like it. It's definitely not metal. I'm not sure whether to clean and reinstall which probably isn't smart or get a replacement kit. Speaking of replacement kits, should I get one of the carbon kits or an 18 plate steel "street kit"? any one have any experience with either? I want to be able to auto x and rotate the rear but I also don't want it to sound like the car is falling apart around turns. Any advice would be awesome.  

And a pic of my car for the hell of it. ( I love my new wheels ) IDK if their knock off's lol.

Upon a second inspection I do believe their steel, just with a coating on them that is worn away. 

I've had a fresh Eaton with really tight clutches chatterd around corners. Could you be confusing that for a clunk? I remember having to add a friction additive to the gear oil. Could that have been missing?

In reply to Appleseed :

Hey thanks for the reply. I did do a fluid change in it in 2014 to try and solve the issue. I don't remember what gear oil I used but I do know I put one full tube of Trans X Posi Trac additive. Maybe that wasn't enough? I've been reading on some other sites that some people have had to use 2 bottles of it. Maybe that is my the whole issue.

What gear oil and additive did you use?

Not sure. I did get the pumpkin, additive, and ring gear for the 8.5 in the back of the 9C1 from Randy's Ring and Pinion. Wish I could remember, but that Posi was installed over 17 years ago and the car is long gone. Any way you could contact Moser for help as its likely that the 12 bolt was delivered as a complete ready to drop in unit.

I had a customer who had another shop put one of these in.  It barked and popped and was generally unpleasant as all hell when you were at neutral throttle.

Given that he only ever had allseason tires on the thing, having tons of preload made no sense.  I took the diff out and inverted a clutch and steel on each side.  So it would be for example SCSCCSS instead of SCSCSCS.  It still had plenty of limited slip action for the low grip tires but it was a lot more pleasant.  I might have removed the preload spring as well, it's been a while.

Mazda did this on the RX-7 GSL-SE to make it more pleasant to live with.  The base model cars with limited slip were almost unbearably tight, and they would pop and bark and be unpleasant.

In reply to Appleseed :

Thanks, I just wrote Moser an email to see what they have to say. 

In reply to Knurled. :

Yes exactly! It happens at "Neutral Throttle". That's the phrase I've been looking for. 

Well I have Firestone Indy 500's. Not really a track tire but not all season either. I actually just watched a YouTube video of a guy rebuilding a mustang diff and that's how the stock clutches came out. I thought there must of been a mistake but it makes sense now. Well I think I will order new clutches and see if that does it and if not I will most likely try what you have said about inverting them. 

In reply to PatM211 :

Even with them inverted, accelerating gently in a tight corner would make the inside tire spin.  So it still had tons of lockup.

So doing more research I found an article on Hot Rod Magazines website. Apparently I have the 800lb pre-load springs and I'm 90 percent sure they are steel plate clutches (no coating) . I think the 800lb springs may be the culprit causing the clutches to wear so fast since they are only for drag racing, not really street driving. 

I think I will order 400lb springs and carbon clutches tonight. 

Article for anyone looking in the future. https://www.hotrod.com/articles/gm-12-bolt-rearends-freshening-a-posi-is-cheap-and-easy/

i had a similar issue with the ford 8" in the mustang, it would be fine after sitting but drive a few miles and it would chatter in parking lots and tight turns.  turns out mobil 1 gear oil doesn't have enough friction modifiers in it, and 6oz of additive fixed the issue.  since you have it apart already i'd go ahead and put the new parts in it.  

Knurled. said:

In reply to PatM211 :

Even with them inverted, accelerating gently in a tight corner would make the inside tire spin.  So it still had tons of lockup.

(EDIT: I'm not going to delete my post so that it may stand as a warning to others that being caffeinated doesn't mean being on your game, but like the ramblings of Billy Madison, I advise anyone who wishes not to become dumber to just skip it. There's no useful information here to glean.)

Oh god. I've just had two cups of coffee and it's mid-afternoon, so if I'm being dumb it's just... me.

Do you mean that on gentle acceleration it locked up enough that it started dragging the inside tire? Spinning the inside tire sounds like lack of lockup, but I also wouldn't have associated that with gentle acceleration...

In reply to Ransom :

I'll let you picture what happens in, say, a zero turn mower, and reflect on your actions. 

In reply to Strizzo :

Yes exactly, like when pulling into the gas station. Okay so I wont use Mobile 1. Ill probably just go with a conventional gear lube and 1 bottle of modifier to start then add another half or so if its still doing it. 

I agree with not putting used pats back in. I would probably be kicking my self down the road for it. I ordered carbon clutches and 400lb pre load springs tonight.

I'll report back when I get it all together. Hopefully summit doesn't take to long to ship being the holiday weekend.

In reply to PatM211 :

FWIW, on my customer's car, we tried all sorts of different oils, and sometimes as much as twice the recommended amount of friction modifier.  It was just harsh no matter what.

Now that I remember it a little more, it didn't have an S-spring, it had a serious collection of F.U coil springs, so I put them back in as-is.

The other thing that helped a lot was I took out the rod end trailing links that the other shop installed, and installed links that had actual bushings in them.  NVH went down dramatically.

In reply to PatM211 :

yeah, I could hear the outside axle popping as it was driving the car on the locked up inside wheel and then jumping ahead as the slack came out of the spider gears/ axle splines.  the lower preload should make things a lot more driveable while still being able to limit wheelspin on course.  

Knurled. said:

In reply to Ransom :

I'll let you picture what happens in, say, a zero turn mower, and reflect on your actions. 

I think the coffee was defective.

Eaton-style clutch diffs LOVE trans-X... lots of it.  Especially with 800lb springs.

Two tubes.  All of it.

Also your wheels are knockoffs - the lips are wrong to be real.

You can look behind the bolts around the OD of the face and see if they have nuts on the back side.  That would be the smoking gun.