Does anyone know if there is any test (torque reading) or whatever to tell if the clutches need replacing in an 8.5 GN posi-trac rear assembly? We removed the cover and everything looks very good, no seal leaks, gear surfaces look good, no excessive backlash.
8.5 GN rear posi Test?
- Thread starter Tom Lambert
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Interesting to read the replies.
I went to Aurora, IL in c. 2011(?) to look at 1 I found on ebay. My dad asked to spin off diff cover to make sure nothing was totally busted. The guy (owner of Silver Bullet) laughed at him and said, "these rear ends are indestructible" but relented. We pulled cover and it was not a posi. I about died. This guys dad owned a buick dealer back in the day. He had a checkerboard shop, the 'Silverbullet', a fully fiberglass GN, about 2 other GN's, and then blamed it on his "parts guy" for advertising it as a posi.
To add salt, I ran a toll outside of Chicago with an empty bedside a wallet full of $.
With that, I interested to hear replies to his question after hearing about their strength.
I went to Aurora, IL in c. 2011(?) to look at 1 I found on ebay. My dad asked to spin off diff cover to make sure nothing was totally busted. The guy (owner of Silver Bullet) laughed at him and said, "these rear ends are indestructible" but relented. We pulled cover and it was not a posi. I about died. This guys dad owned a buick dealer back in the day. He had a checkerboard shop, the 'Silverbullet', a fully fiberglass GN, about 2 other GN's, and then blamed it on his "parts guy" for advertising it as a posi.
To add salt, I ran a toll outside of Chicago with an empty bedside a wallet full of $.
With that, I interested to hear replies to his question after hearing about their strength.
if its in the car do a burnout
If it;s not, push and pull on the axles, check the wear pattern on the ring gear
Eaton posi has 400# springs pretty much impossible to hold one wheel while someone else turns the other
If you can do that the posi is no good
If you changed the oil make sure you use at least 3 bottles of the ACDelco posi additive or you will get massive chatter
If it;s not, push and pull on the axles, check the wear pattern on the ring gear
Eaton posi has 400# springs pretty much impossible to hold one wheel while someone else turns the other
If you can do that the posi is no good
If you changed the oil make sure you use at least 3 bottles of the ACDelco posi additive or you will get massive chatter
A set of drag radials or slicks and do a burnout. Have some one watch for both tires to begin spinning together. Oce it starts spinning, allow the car to walk ahead slowly and then see how similar the marks are.
In terms of breakaway torque, I'm not aware of a particular number/spec. IMO you should not be able to turn a wheel with one side in the air on a jack and the other on the ground and the car in park using.
Why not just tear down the diff and inspect the clutches?
In terms of breakaway torque, I'm not aware of a particular number/spec. IMO you should not be able to turn a wheel with one side in the air on a jack and the other on the ground and the car in park using.
Why not just tear down the diff and inspect the clutches?
Some of the T-Types and GN's came with an open rear assembly, you had to check off G80 to get the posi. We bought two assemblies from Nick in Phoenix, mine was an open, I rebuilt and installed a posi, the other one is for my son Pat. It is the one I'm asking about, it has the longer wheel studs so was run on the track at some point. I we hoping we could install new seals and wheel bearing and be good to go!
if its in the car do a burnout
If it;s not, push and pull on the axles, check the wear pattern on the ring gear
Eaton posi has 400# springs pretty much impossible to hold one wheel while someone else turns the other
If you can do that the posi is no good
If you changed the oil make sure you use at least 3 bottles of the ACDelco posi additive or you will get massive chatter
Thanks Turna, will do. The rear is out of the car.
You can install new wheel bearings and seals, and then go. What's the worst that will happen, one wheel peel in the burnout box? I'm always much more concerned about the carrier bearings and gear set being pitted from rust caused by condensation.
All I know is people tell me they are good through about 400 horsepower before they start acting less posi and more open. As i upgraded my motor over the years to make more power, I can tell you this is definitely true. I got rid of the 411 case factory posi and now run a True Trac with Moser 30 spline axles and am very happy with how it drives and handles.
Oh yeah be careful with him as I hear and now he has a shop in downtown Lemont has his kid running it
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