Racers - G80 or "True posi" ?

[dsa87gn]

Just wondering who sticks with the "G80" option rear end
or converts to a "true posi" rear end , and opinions on it...

 

[GNVAIR]

The G80 is an Eaton limited slip differential. Posi and Limited slip are the same thing. Posi is just a GM name for it. Much like Traction Lock is Ford's name for it.
If you mean a "locked" differential, then you would be referring to a spool.

 

[gnturbo]

or a detroit locker as in "locker".The rear "posi" I have seen pulled outta the rear of a gn does not look as beefy as the eaton I just put in my car.There is also the ARB air locker that is open until locked via air pressure.I don't know of arb makes a air locker for the 8.5 but they make one for the 10 and 12 bolt truck rear ends.Also there is the "ox locker" which is a cable acuated "locker "that is very beefy.

 

[WarpSpeed]

Welp, my Limited has a G80(stock posi), and my GN has an Auburn I installed. In my opinion the Auburn(or Eaton aftermarket probably) provides better traction whether racing or in bad weather. Let's put it this way, I used the GN to pull the stuck Limited out of the snow in the front yard. It seems when the stock posi spins the tires, it actually breaks one tire loose at a time,, I'm guessing because the clutches have to tighten or something. With the Auburn, you have to break both tires loose at the same time for it to spin,,, even in turns it doesn't spin the inside tire like the factory posi...

 

[TurboDave]

Originally posted by WarpSpeed
Welp, my Limited has a G80(stock posi), and my GN has an Auburn I installed. In my opinion the Auburn(or Eaton aftermarket probably) provides better traction whether racing or in bad weather. Let's put it this way, I used the GN to pull the stuck Limited out of the snow in the front yard. It seems when the stock posi spins the tires, it actually breaks one tire loose at a time,, I'm guessing because the clutches have to tighten or something. With the Auburn, you have to break both tires loose at the same time for it to spin,,, even in turns it doesn't spin the inside tire like the factory posi...

What you're experiencing is a problem, NOT normal operation for a G80 unit. You've likely got some worn clutches, etc. It's really unfair to catagorize the way your G80 operates as "normal G80 operation". It's really not.

In the situations above, a normal operating G80 would apply the power to the wheels exactly as your Auburn unit does.

 

[GNVAIR]

The stock limited slip carrier was manufactured for GM by Eaton. I have an after market Eaton I installed in my truck. The only differences I can see between the stock one in the GN and the after market is the GN uses an "S" spring to preload the clutches and the after market uses actual coil springs. The after market has much more preload. But as TurboDave said, if you are able to spin the wheels that easily then most likely you have lost the preload on the clutches. They are most likely worn out.
The stock Eaton on my GN will actually chirp the tires going around turns. The problem with the Auburns is that they dont not like shock loading and IF you spin one wheel when doing a burn out, you will quickly wear the cones out. The Auburns are also NOT serviceable; which means when they wear out, you can pretty much make a paper weight out of it since Auburn Gear will not sell service parts for them. If you want to see what 1.4-1.5 60 foot times do to an Aurburn, stop down this way. I have quite a few blown up ones from some of the Mustangs I have worked on. The Eatons on the other hand can be rebuilt with new clutches AND worst case scenario; side gears and spider gears.
True the Detroit Locker is a ratcheting type differential, but in my experience from working on them (the 4x4 guys used to use them), they arent what they are cracked up to be. All of the guys I have done rears for have problems with them not unlocking when going around turns........basically you have a very heavy and expensive spool. Its an inherent design flaw.
The ARB air lockers are a different set up. They dont differentiate when locked. They are either "open" or "locked"
No in between. I try to steer all of my customers towards the Eaton since it is by far the most reliable and durable limited slip differential you can buy. But I only recommend it after finding out how the car is driven and what it is used for. I still recommend full spools for cars that launch very hard (sub 1.5 60 ft times) or very heavy cars.

 

[GNVAIR]

Originally posted by ILBCNU6
I don't know who built the stock posi for GM. The corporate rear end in a TR has what is called a gov-lock and actually disengages itself at rpm. The true posi's don't do this and like the GM posi-trac of the late 60's and early 70's. An air locker would be great however it would be a one wheel wonder whenever unlocked! My first GN I tried this by running it with only one wheel planted on the ground and only one wheel pulled, the one elevated, not the one on the ground. You set them by using shims and a torque value to break loose. A junk rear end because of being a Corporate Model, flimsy rear brake backing plates and wheel cylinder mounting, and C-clips axels! Just look at a real rear end, like a 70 GS Stage 1, big axel tubes, big axels, solid backing plates, and bolt in wheel cylinders. A Buick built part not a Corporate Type! However the TR rear end is much stronger than any other in its time including the new F Bodies! Gene

Gene,
I have 3 stock TR 8.5's and they all have Eatons from the factory. They are almost identical to the ones Chevrolet used in the early 8.25 10 bolts and the 65-72 passenger car 12 bolts.
If my memory serves me correct, it is even noted in the 87 Buick service manual that Eaton was the manufacturer.
All of the 8.5 TR rears I have worked on (and it is probably pushing 50 some cars) had the Eaton clutch type limited slip.
The Gov Lock was used in 8.5 equipt full size trucks. The gov lock used a combination of clutches between each side gear and the carrier with a rather intricate mechanism that would have a ratchet arm that would fly out and lock the side gears together under load. I have NEVER seen an TR or 442 8.5 10 bolt with one.
GM doesnt even list it in the service manual. If you have/had one, then someone put it there.
Here is some info I found on the Gov Lock:
n the early seventies real muscle cars were fading away, and average (boring) Americans were becoming more concerned with a plush ride than high performance. In the 1973 model year General Motors decided to start using the Gov-Lock in trucks in an effort to eliminate positraction chatter associated with conventional spring preload clutch type positractions. This was the one of the few solutions available using 1970's technology. Thus, for GM trucks produced after 1972, the only traction enhancing option was the Gov-Lock (still produced by Eaton) which does not even begin to compare to Eaton's four spring Positraction. These governor actuated units provide a locking differential without chatter. Great for the average truck owner, but not for those who really use their trucks off-road. Often referred to as a "time bomb" or "Timex Posi" (no disrespect intended Timex, just as watch size parts were never intended for use in a differential). These locking differentials work fair for occasional use when traction is of small concern, but not when power transfer and traction are the main goal.
The Gov-Lock can fail in any number of ways and often does. Usually the case will break in half, but sometimes small internal parts will break. I have no intention of defending them except to say that the Gov-Locks used in 3/4 & 1 ton trucks hold up fairly well due to their sheer size, and especially well when compared to the smaller designs.
For readers looking for something stronger, Eaton makes redesigned units that they can be very proud to show off. They are not actually a "new" design as much as they are the old design, with a whole lot of improvements. The basis for their new units is the heavy duty positraction that they originally produced for big block GM muscle cars in the sixties and early seventies.
The 64-72 Buicks actually shared rears with the Pontiacs. They did have bolt in axles, but still had a small 8.25" ring gear along with a lousy conse style differential. The 70 455 Stage 1 cars actually used the Chevrolet 12 bolt, as did the 70 Pontiac GTO's with their 455's.
I am not trying to step on anyones feet or start a flame war. I am just trying to state the facts since I have been rebuilding rears for many years.
Bottom line is the stock Eaton posi in the TR rears is a great set up and very easily rebuilt. You can upgrade the stock 8.5 with bolt in axle shafts now. Mark Williams and Moser both sell kits to do so. The Mark Williams allows using the bolt on 64-72 rear drum brakes and wheel cylinders. This is the set up I will be installing on my Malibu.