8.5 GN rear posi Test?

[79 USA 1]

My 79 GM shop manual lists a rotating force of no less than 40 ft/lb using a 0-150 ft/lb torque wrench after rebuild of an Eaton unit. Does not give a number for a in use unit.

 

[spidereyes455]

 

[64nailhead]

View attachment 134169

Wow! 35 ft/lbs - never would've guessed that low. I have to admit that I've never messed with a factory posi, and I should've mentioned that in my previous post, but the Yukon 8.6 I have in our 8.5 housing won't move with well over 100 ft/lbs applied.

Great info though - thanks!!

 

[64nailhead]

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.

We have a Yukon posi that we put double 400HP through that works very well. I would find it hard to believe that a factory unit won't hold 400HP. But anything is possible I guess.

 

[Tom Lambert]

I want to thank Everyone for the quick response and information. I didn't think about it but I could have run the torque test on my Cutlass in the garage, it has a new posi and has not been driver yet. I will run the torque test and let everyone know the results on a new unit.

 

[pontiacgp]

Wow! 35 ft/lbs - never would've guessed that low. I have to admit that I've never messed with a factory posi, and I should've mentioned that in my previous post, but the Yukon 8.6 I have in our 8.5 housing won't move with well over 100 ft/lbs applied.

Great info though - thanks!!

they come light from factory so the clutch packs don't wear out fast. They have springs kits that increase the breakaway torque and you can get carbon fiber clutch packs now.,

 

[Firetruck1]

We have a Yukon posi that we put double 400HP through that works very well. I would find it hard to believe that a factory unit won't hold 400HP. But anything is possible I guess.

Yes, stock they are made for comfort and idiot proof driving characteristics. Even performance cars were (and still are to a degree) watered down.

 

[Pronto-]

Good thing you looked. Something else to consider, my t came with an open diff. We put in an Eaton. Sucker is tight as a virgin. Without drag radials it will squeak the tire on a tight turn in a parking lot. Never fails to leave equal stripes. One of those will not fail in your car. Seen them go low 9s dozens of times. Cone style posi's are known to wear out, especially if you do a burnout half on dirt and pavement. One wheel will spin and one won't as the cone gets glazed. If you jack the car up and spin the tire by hand and the tires rotate opposite directions then it's open or a failed posi.

 

[pontiacgp]

Good thing you looked. Something else to consider, my t came with an open diff. We put in an Eaton. Sucker is tight as a virgin. Without drag radials it will squeak the tire on a tight turn in a parking lot. Never fails to leave equal stripes. One of those will not fail in your car. Seen them go low 9s dozens of times.

the stock preload springs are 400 lbs, you may have had the 800 lbs preload springs

 

[69hurstolds]

Yes, stock they are made for comfort and idiot proof driving characteristics. Even performance cars were (and still are to a degree) watered down.

Of course. They have to be. General public would scream bloody murder if their street car chirped and chattered going around a corner. And I know because I did. I took my 85 442 back to the dealership because it chattered going around the corner. Apparently not enough or no anti-slip additive from the factory. Added a bottle under warranty and I was on my way again.