I recently bought a 91 Z28 with 132,000 miles. I thought all Z28 had posi. The RPO sticker says it's posi. When I changed the rear end oil (that was dirty so it's been a while since last change) it has an open carrier. And some heavy gouges in the carrier from what looks like the pinion gear came loose and came in contact with the carrier. It appears to have been fixed meaning it does not make contact now. What do you think happened and why do you think it has an open carrier?


This is a street only car for cruising and yes I will tromp on it once in a while but not regularly. I want to install a posi clutch type carrier. I'm leaning towards an Eaton. What's your thoughts on Eaton vs Yukon? What do you think of this one? https://www.ronsmachiningservice.net...grip-posi-lsd/ It doesn't say it's an Eaton but it takes Eaton type parts, it's rebuildable and I like the price. Thoughts?

 

Looks like the pinion yoke nut backed off. When the torque is in the forward direction, the pinion tries to push itself out the front of the housing (which is why the rearward pinion bearing is bigger); in reverse, it tries to suck itself inwards, and the nut is what keeps it from ... doing that. When it backs off it lets the pinion get sucked into the rest of the guts like that. Pretty common really, in and of itself, doesn't really hurt much, except for filling the fluid with metal chips.

However I'd be concerned about whether that was "repaired" (new bearings, seals, shims, etc.) or just "fixed" (tightened the nut). I'm not too sure I'd just put another carrier in that without a bit more due diligence.

Also, in 2022, the Eaton type carriers, with clutches, introduced in the 60s, are kinda ... obsolete. I'd recommend a Torsen or TrueTrac which are worm-gear (clutchless) systems. You can get a used Torsen out of a LS1 Camaro or Firebird. Extra points if it's a SLP (a heavier duty one): SS or WS6.

Definitely NOT the one you linked to. "Assembled in the USA". Just exactly what do you suppose THAT means?

 

Not sure what year Camaro you're referring to, but my 2002 1LE/SS/SLP for sure doesn't have a Torsen diff.

 

Ok, so you suggest this one? https://www.summitracing.com/parts/dtl-912a317
All the teeth on the ring & pinion gears looked good. No marks/chips. I plan on using the same gears unless I find an issue when I get it apart.
When I change over I will change ALL the seals & bearings: carrier, pinion & outer axle bearings.

 

Ok, so you suggest this one? https://www.summitracing.com/parts/dtl-912a317

 

It's all based on one question IMO, what's the usage of the car. You stating: street car with some stomping on the gas pedal, means there is nothing wrong with a clutch type differential from Eaton or Yukon.

Clutch type differentials still provide the smoothest operation with good locking action when needed. Just stay away from Auburn as those differentials are not rebuildable/upgradable at home, where the other two are.

There is a place for other type of differentials and there is nothing wrong with installing them in your car. If you ask me, are these the best bang for you $ in your application, then my answer will be NO.

 

I certainly wouldn't reuse those gears. Wall art!

 

Would you put in a TrueTrac type or what and why please?

NoEmissions84TA
I certainly wouldn't reuse those gears. Wall art!
Why please?

 

Time for an S60 rear end to tame the 350 TPI

 

1) Because there could be damage that you cannot see.

2) You are going to be replacing the differential, bearings, etc. anyways. The only thing left is the gears, and the gears are cheap compared to the rest of the parts. Why would you want to gamble and risk all of the money and work you are going to put into this, and then the R&P gears decide to come apart - possibly destroying everything.

3) It has been said before, but here it is again..... If you are going to spend your money, get an UPgrade in the process, not a DOWNgrade.

 

Hind sight. I'm changing all the bearings/seals for that very reason. It's nice hearing from more knowledgeable people for guidance. Thank you.

 

Starting a full rebuild of a 8.2 rear next week. Took me some time to convince the owner to get new axles as well after seeing the old ones with bearing surface damaged by old old bearings. First he wanted to run them as is, then me to install a repair bearing, finally he's doing the right thing.

 

I'm going to pull the axels and look at them (bearing area) before I order an parts. Make sure what axels/splines I have before I order a carrier for them.

 

Yeah, axles are a real problem in old rears... stock ones tend to be made out of metal about as tough as butter, and sometimes even ones that "look" "good", have other issues. Bent, out of round, lugs drilled off-center, poorly made splines, ... you name it. Especially parts from the 70s. Those were the worst years for "quality control" in the US automotive industry, fodder for many a MBA case study I can assure you.

BBC, if you do need axles (and you DO, no matter what the stock ones "look like"), get 28-spline stuff, no matter what's in it now.

 

When I swapped my carrier I got summit house brand axles Sum-700118 28 spline. I have rear iron delco calipers and could not get my rotors over the axle hub the axles fit great in the housing and the differential. Unfortunately I had to turn the outer hub about 0.300". The Bearings are they came with were koyo and made in japan no issues there.

No regrets ended up finding a guy to machine them after work for a $10 and I got to clean the lathe.

Edit
Just looked again you have a 91 so that is 28 spline factory. Get some good replacements and you will be good to go.