Posi Rear Help

I have a 71 GSX clone with a BOP rear diff. 3:23 gears. It is a posi rear, not an open differential. I was told this is a cone type posi. So I guess it is an Auburn rear. The guts of the diff are original. The posi is only working part time. My questions are :

1. I have royal purple gear oil in it. Could it be too slick, not letting the cones lock into the housing and are possibly slipping? (Hoping for a cheap fix)

2. If the posi housing is worn out, what is the cheapest & easiest way to fix? Another cone type Auburn unit? An Eaton clutch style posi? Eaton posi $600, I found a new Auburn unit for $312.00.

3. Is there any way to fix the existing unit?

4. What do I look for when I remove the cover?

Any help would be greatly appreciated....Thanks.

:3gears:

 

Ok, well the cheapest fix right now is the flush that rear out with some brake cleaner the best you can and then refill with standard mineral fluid and the proper posi additive. cross your fingers and hope for the best.

If not good still then we have to evaluate the problem. usually the passsenger side cones bottom out first that is the tightes corner when turning so it takes the most wear and tear.


We can go through your exsisting posi and see how bad it is cut the cones and reshim the unit to give it back some life. How long it will go on is all determined on your driving manners too.

How bad is the posi NOT working...??? now and then all the time etc. Jim

Removing the cover will not really reveal anything to the extent of the wear on the unit. It you see metal parts in the housing then obviously you have some series issues...lol. Highly doubt you will find that the way you explained the trouble. Jim


New Auburn for 312 sould like a pretty darn good price. MAybe even unrealistic...be careful. who might that be from? vendor? Ebay? other?

Do you have pictures of the rear cover area of the rear and the yoke area ? then we can ID the rear so you know exactly the diff your dealing with. This is one of the biggest hurdles to get around. Alot of guys are told or expect they have a certain rear because of the year of the car. after 30-35 years parts are swapped and changed so it may not be what you expect under the car.

I can beat the Eaton price for sure. Double check that Auburn though...I can not even touch that. Jim

Here is what a picture of a reconditioned posi looks like from us jdrace.com

other pictures are in a thread called positraction rebuilding in this GOT GEARS section. Ok? Jim

 

If you put just Royal Purple in it thinking it no longer now requires the GM posi additive it may feel like it is engaging and then releasing over and over.


Drain some RP and squirt in the GM posi additive. Then recheck after you drive it a bit.

 

Thanks for the help, when I put the rear in, I was told that for a cone type posi, I didn't need the posi additive. I guess "they" were wrong. I will try mineral gear oil & posi additive first. Tom's Differentials has the unit for $312.00. My existing unit works on the passenger side more often than the driver's side. If I were to launch it with the front wheels straight, the right side will spin at 100% all the time, the drivers side 20% or not at all at this point.

I have heard that it is not that difficult to replace posi unit if not replacing gears(pinion & ring). I do have some mechanical ability and an ultimate set of tools. lol (Spicolli).... Is it possible to measure backlash, pull axles & replace unit with diff in the car? Making sure that I r&i the shims where they were originally?

o No:

 

GSX...can you add at your first name to your signature line.....would also be helpful if you add your city/state to your header/title bar info.

Your best bet......get rid of the 8.2 and get a corporate 8.5" from a 71-2 Cutlass/Skylark or from a rear axle builder and you will be set. The gears, bearings, axles, seals, posi units are cheaper and you will have more selection than the 8.2".

When going to the 8.5" shorten your d-shaft 1" and you will be set. I would suggest you take it to a pro to have the rear set-up as it takes some experience and special tools to properly set it up....otherwise you are going to get a "totally wasted" (Jeff Spicoli would say) rear.

 

In my experience they were mistaken.

 

Thanks again, I trust you guys more than anyone else. I am going to try non synthetic oil & pois additive & see what happens. I bought this rear from a guy with a 1971 or 72 Cutlass. This may be an 8.5 rear. I just bought a gasket for it & the 8.5 rear gasket is the right one. I am going to take a pic of the rear diff cover & post it.....

See attached photos. Can anyone tell me what size rear this is ???

o No: :3gears:

 

Appears to be an 8.5 rear.
Rear u-joint should be held in place by 2 straps and 4 screws.

 

That's how rear of driveshaft mounts. 2 straps & 4 screws. Can anyone else confirm this is an 8.5 rear? It's not that I don't trust you, I just want to make sure, so I odrer the right parts when needed.

 

A 68-70 Buick 8.2 does not mount that way.

 

Anyone out there know of a good rear guy near the Philadelphia Pa area? I need to find someone who is reliable to rebuild my posi unit. My worst fear is paying to have it done & it blowing up.

I live in West Chester, PA. South of Philly, not too far from Delaware, about 1hour north of Cecil County Dragway.

 

GSX-Rated you gave me flashbacks of years ago when I put a Auburn cone diff in my 85 GN. I purchased the unit because it was cheaper than the other brands. Thats where I went wrong!!! Within 8 thousand miles guess what? My Auburn started doing the same thing, sometimes it worked and sometimes didn't. I again learned a valuable lesson you get what you pay for. I have been an Eaton man ever since. I think your wasting your $$$ to rebuild it because your problems will just come back again.:dollar:

 

You're right. I am going with an Eaton. I may try to install it myself, if I can't find a reliable guy around here.

 

Hey Jim, (flynbuick) I'm guessing this is a 28 spline axle differential? 30 splines came later? Or do I have that backward?

 

Thanks, Larry.