I don't know that much about what the G80 option was other than "limited slip" on our cars.

My driveway is frozen over right now and I was moving the car and was going to take it for a spin today-- nice dry, sunny day here in the northwest with clear, dry roads. The car got stuck in the driveway though on the compact snow/ice. Couldn't get both rear wheels to hook up. The rear axle is original, with limited slip, as far as I can tell--RPO and tag on rear diff both say yes. But I think it might be worn out. It was behaving like an open diff.

What's it take to rebuild/replace the clutch in those?

 

Assuming your car still has the original 10-bolt with the Auburn crap:

Pretty easy, really...

All you need is, a new carrier. Something better than an Auburn.

The clutches and other internal parts in those POSs are not serviceable.

 

30 years later, yes, the posi/limited-slip clutches are probably worn out.

However, a "limited-slip" does not give you "two wheels turning all the time" like a locker or spool. If one tire has good traction, the other has none (on ice), and the posi is only good for 100 lb-ft, when you try to apply 200 lb-ft of torque to go, you overpower the posi's bias and spin one tire.

 

Car only has 60k miles and according to the previous owner, was not abused (whatever that means). So was hoping it was still functional, but maybe the clutch material just degrades over time?

At any rate, what does replacing a carrier look like? I've only ever changed fluid in a differential before. I've heard gear swaps and other diff work is rather involved. Sounds like I'll be going to a shop unless a "carrier" comes in a box and is bolt-in and includes everything.

 

The Auburn differential that was used in these cars does not have replaceable clutches. It has cones that fit into tapered holes, and all of it is steel. The material does not degrade, it just wears away. The Auburn differential is not rebuildable, so when it wears out it's scrap metal.

It's possible that you just didn't have enough traction to the tires to allow the unit to lock up. These differentials were not designed for snow and ice, they were designed to give power to both tires on blacktop. You need a little bit of traction to the tires for it to lock up well. So it's possible that the differential is fine, just not working under these conditions.

If it is worn out then you have to replace the complete differential. Don't get another Auburn. Get a Eaton Posi, Eaton Truetrac or a Yukon Dura Grip. Anything but an Auburn or a Eaton Governor Lock. This is NOT a bolt in job. It requires some precision measurements and shims to set the bearing preload and backlash.

 

Thanks for the info.

So...a better test for the original rear axle... find some smooth, dry asphalt, bury the gas pedal in 1st gear, see if the tires leave two stripes, not one?

I've never done that in the Iroc--the 700R4 is also original and I'm just not quite ready to pull everything out to have it rebuilt.

 

Best test is, take off the cover and look. There is NO SUBSTITUTE.

 

Testing your posi / limited slip diff...
Block the front wheels (safety first!).
Jack the rear tires off the ground.
Parking brake off.
Trans in park.

Can you turn a rear wheel by hand?
- If yes, does the other wheel turn in the opposite direction?
- - If yes, posi is worn out.
- - If no, you did something wrong. Either the drive shaft turned, or the other wheel will.
- If no, posi still has some life.
Put trans in neutral, turn rear wheel by hand. Which way does the other wheel turn?
- Same way, posi may be OK.
- Opposite direction, posi is worn out.

 

mine had a mind of it's own.

 

By default, an auburn is, like any friction based posi, holding both sides together until force exceeding the holding power of the cones is reached. MoJoe described it above. Since an OEM application is supposed to drive on the street and turn, they didn't set them up tight, and turning a corner should go somewhat smooth.

Since I also have a 1986 OEM GM 3 series 7.625" Auburn posi that works fine with over 150'000 miles, I suggest you
- Do the test in post #8 ( this doesn't work on the base-design Torsen differentials, only friction based posi units)
- then the test in post # 7 to get fresh lube in. I think it is 80/90 but check. Also, some G M posi additive;just a little bit not the whole bottle.
- then the test in post #6
If it is working, but too tight, add more additive.
If it just isn't working, start saving and planning ahead.

I am not pro Auburn, but I don't junk stuff that is still working.

 

Yes sir - Agreed. I had the cover off for a fluid swap about 250 miles ago. Wasn't sure what I was looking at other than that the gears were there and things appeared to be in good shape.

Ah. Sounds like I need to investigate further this weekend.

Will complete tests. Already swapped lube ~250 miles ago, had cover off. Gears looked good- but wasn't quite sure of what I was looking at. Fluid was at proper level before draining it. It was dirty, but not neglected. No hard chunks or metal at the bottom, just thicker, blacker goo.

 

Lol...you got landing gear on that thing? Where did the 3rd wheel come from? Haha

 

that was the same car, same tires, same rear, within a very short time period. sometimes the posi worked, sometimes it didnt. i changed fluid and used the posi additive fluid. it never got better, only worse as time went by. and i jacked one side of the car up and it took some good force to turn the tire. jacked both wheels up and they booth spun together. definetly a posi carrier. mine ended up chunking pieces of the spider gears eventually. maybe its the nature of the beast? just sharing my experience. i cant comment on the ice because we never get any, lol

 

Joe, you probably broke the gears because the cones were worn out. As the cones wear they sink farther into the case, which increases the space between the axle gears. This causes the axle gears and the pinion gears to run farther out toward the ends of the teeth, which makes them very weak. This is a common problem with the Auburn.

 

sounds like thats what happend BGH. i can get 3rd gen, factory 10-bolt posi rears from a guy locally here for $100 all day long. not even going to waste my time. i'm planning on trying the true-trac. mostly street driving, occasional racing. any opinion of the true-trac?

 

The only thing that I have installed the Truetrac in is the front of 4X4 trucks, so I don't have any good personal experience with them. I have installed one in a '69 Mustang, but that one isn't on the road yet. All I Can say is what I have learned from others. Some say that they don't always lock up when doing a burnout. Others say that they work perfect. My opinion is that they are better for auto cross and road racing because they won't upset the car when they slip when going around a corner. I prefer the Eaton Posi ir Yukon Dura Grip for most street/strip use.

 

i appreciate your experience, knowledge, and honesty. I've also heard something about the true-trac not locking sometimes unless you roll backwards first or something. IDK, maybe i should save a few more pennies for a better carrier? i'm kind of leary of the clutch type posi for some reason? thats why i was leaning towards the true-trac.

 

What will you be doing with the car?