TSM I did not mean to imply your son didn’t listen. I was responding to the OP’s comment.
You guys are completely off topic. Lmao
No problem, Volvo.
Bambsbamsbino, that may be true, and if I misunderstood I apologize. I sincerely hope I did misunderstand.
I never said the vehicle had a Detroit Locker.
I just referred to it as an example on how a LSD worked.
The OP also states that the previous owner installed the LSD.
So it can’t be a Detroit Locker?
Tester
@JWB has some good comments above. My 40+ year old Ford 4WD truck has limited slip differentials front and back. I replaced the clutches in the rear diff a few years ago. That’s the main difference b/t non-limited slip and limited slip designs, the LS has the clutches. I’m not familiar with posi-trac so everything I say here is just a guess of course, but I’m presuming (i.e. guessing) GM’s posi-trac design is similar to Ford LS.
To change the clutch pack I had to remove the rear axels, and I don’t recall there being a 1/4 inch of axial play in those. But I could just be guessing about that, not remembering correctly, as it was a while ago. In any event my guess is that the axial play isn’t what’s contributing to the problem here.
I’d guess instead it’s either the clutches are worn out – not an uncommon problem with LS’s – or the gear oil doesn’t have the correct slip parameters posi-trac requires. On my Ford I have to add some extra stuff , friction modifier they call it, I get it at a Ford dealership. I add it to the standard gear oil in the diff, so that it slips correctly. You might not have enough of it, or too much of it, or not the correct kind for your differential.
I had a discussion on this topic with my auto parts staff and they – have a lot of experience w/4wd crawler hobbiests – they said a lot of folks prefer to use the Chrysler friction modifier rather than the one recommended by their own manufacturer. It might pay to look into that.
One thing you could do it simply change the differential fluid. That might work, or you might find some metal parts come out indicating the diff needs some internal fixing.
But of course I haven’t actually seen your car, and no experience with posi-trac, so this is all just a guess …
The Art of the Guess, By George
“posi-trac” is the GM name for whatever limited slip diff they slapped in there. Usually clutch-pack types, sometimes friction-cone types depending on who made the diff. GM trucks have used Detroit Locker ratchet type diff and a modified version called a Rev-Loc. The Rev lock won’t engage above about 20-25 mph if one wheel slips. It only works from a standing start or slow roll.
Detroit Lockers, from my experience, hit like a sledgehammer when they lock, straight or turning. I used to get hammered regularly from the Dana 60 rear in my 3/4 ton 454 Suburban.
I’d rather weld up the diff and run locked solid than use a Detroit Locker on a road-race track! (until it rains!)
I had a 67 Buick wagon that I bought for house building that I’d swear the rear end was welded together. The guy had weld marks in a number of places on that car and it was absolutely terrible on an icy interstate. Luckily it never got driven much out of town but it just seemed both rear wheels would spin at the same time and the back end would swerve. Maybe it had the locker or something in it. It sure never got stuck in the snow in town though.
Clutch packs sound about right. Unfortunately just taking off the cover theyre stiff as hell and dont know how to test if they are working properly. Looks like springs complety compressed. I tried moving it. Didnt budge. Didnt want want to start prying on it or anything as this is my daily driver until i get done with my truck.
I drove a Ford 9 inch “Detroit Locker” for about 3 years. You could definitely feel it re-lock and occasionally “growl” when turning a city street 90 degree corner.
Are you certain you have the proper gear oil and friction modifier installed?
Right! The proper additive is critical. I had a Caprice with Positraction and the exact GM specified additive in the right amount was needed to avoid the rear end clatter.
You need a knowledgeable mechanic to add this stuff. Jiffy Lube’s teen aged kids have no clue what you are talking about.
I used to get what they called a bottle of whale oil from the dealer. It came with a short piece of plastic tubing. You just lay under the car, open the fill plug, and squeeze the bottle. No skill required and only takes a few minutes. Then you drive it around in a few figure 8s to distribute it.
We have it at my work. And yes i added it. Its past just needing an additive. That was part of the reason i took the cover off to check it. Digured maybe the guy that put the gears in it didnt know about the additive. Its starting to make a clicking noise when taking off too