Rebuild 8 3/4 SG acts like Spool/stright axle in turns...normal??

[AKcharger]

Hi Guys

I installed a 3:91 in my '70 and there is zero slip in the rear end going around corners, it acts like a spool. I tried doing some figure 8's in a parking lot to "break" the clutches free and the rear end would "hop" (interestingly only when I went to the rt. to the left it just squealed) a Pal said it can take up to 500 miles for it to "break in" is that true?  Before I yank it out anyone have suggestions?

- Unit was completely rebuild in very reputable shop in Alaska 4 years ago, properly stored and oiled.
- Used limited slip lube the shop gave me, no slip at all, so I drained oil, and use the MOPAR additive with new oil...same
- Maybe 10 miles on gear

Anything I'm missing?

[c00nhunterjoe]

Its definatly a clutch style suregrip? There is a breakaway torque spec but i dont know it off the top of my head. Must have packed them babies tight. I like it. You could try some more drive time followed by tight circles to see if it loosens up any. Shouldnt take more then a few miles to settle in if its going to.

[Birdflu]

The break away torque on both the Dana style Powr-Lok or the Borg-Warner cone clutch style is waaay less than the weight of a '70 B-body going around a corner on bare pavement. Do you know which style sure-grip is in the third member? First pic is a Powr-Lok...second is the Borg-Warner cone clutch style...

[AKcharger]

Thanks guys...It's a clutch type for sure.

A little more to the story...The rebuild was actually in 2013. I installed it in the '72 Charger and it did the same thing it's doing now going around corners. So I removed it, brought it back to the shop and they said they "adjusted it" which I'm guessing is the pre-load you guys are talking about. Then We moved down to Florida and Just now got around to installing it. So I'm thinking maybe they put the clutch packs in wrong and they are "locked"??

[c00nhunterjoe]

Jack up each rear tire individually with the car in neutral and see if you can force it to open by grabbing the tire and rotating it.

[AKcharger]

Joe i know your pretty savvy but how would the 100-150 ft lbs of torque I could manualy apply be more than a 4000lb car going in a circle??

[Birdflu]

Joe i know your pretty savvy but how would the 100-150 ft lbs of torque I could manualy apply be more than a 4000lb car going in a circle??

Couldn't agree more! If you truly have the Borg-Warner style cone clutch unit like the second one pictured, they are almost impossible to set-up with that much pre-load. The pre-load springs in the center of the unit combined with some additional shims are the only contributors to adding friction to the cone clutches. I'd be apprehensive to running those cone clutches that tight (even if you do get the unit to break loose during cornering) as the cone clutches will more than likely destroy themselves by means of metal exchange between them and the case.

[John_Kunkel]

There are two different clutch packs for the clutch-type SG, one for OEM and one for aftermarket. If the wrong pack is installed, it will be too tight and won't slip under load.

[c00nhunterjoe]

The loads are applied different. It "only" takes 100 ft lbs to override the clutches, but yet it will hold a pair of slicks on an 11 second stick car. Its a simple test. The other option is throw it away and buy a new one since its been rebuilt twice and doesnt work...

You said it reacts different left to right, thus the test.

[AKcharger]

Im thinking what John said is the case, they used the wrong clutches.  To continued i dont think is gonna do anything.....crap!!!

Thanks for the info guys

[c00nhunterjoe]

I have packed various model diffs extra tight for customers over the years. Try the method i suggested. With assistance, you can also burn the clutches down with 1 tire in the air per side.

[Alaskan_TA]

Original type axle bearings?

If so, it the adjuster set to spec per the FSM?

[AKcharger]

- Joe...sure cant hurt to try...stay for results
- TA ...stock bearings gapped to about .012 if I recall, book says .008-.018

Thanks!

[Rudderguy]

I have the exact same issue with my 68 rt.

What did you find out?

[AKcharger]

I have the exact same issue with my 68 rt.

What did you find out?

I'm out of town till Thursday, I'll try then.

Hey Joe if I jack up one wheel in neutral and get it to spin what does that mean? It's good? It just needs to be broke in...what. It's almost undrivable as it is.

[c00nhunterjoe]

Im curious if you can overpower the packs or not. Depending on the result, you may have to pull it apart and see what has been done incorrectly inside.

[AKcharger]

Im curious if you can overpower the packs or not. Depending on the result, you may have to pull it apart and see what has been done incorrectly inside.

Copy....stand by till Thursday

[AKcharger]

Hi guys  Sorry to say I didn't do the 0ne wheel test thingy just wanted to get it done so cross-canned (cannibalized) the Gears and made the '72 into a Highway speedster with 2:76's. I looked over the 3:91 and compared it to the 3:23 which turns out to be a clutch unit as well...couldn't see any obvious differences? Oh well 3:91 is back in the 5 gal bucket and returns to "IGTISD"

[John_Kunkel]

I looked over the 3:91 and compared it to the 3:23 which turns out to be a clutch unit as well...couldn't see any obvious differences?

I've never dealt with any clutch-type SG's except factory so I don't know what markings, if any, differ on the aftermarket units but the factory units have a date stamped in the right side case and that date would most likely be prior to '69.

[Kern Dog]

I read that There is an offset built into the clutch plates. If turned the correct way, the unit works normally. If reversed, there is additional tension, AKA friction/preload between the plates and they may act as described here.

[AKcharger]

I read that There is an offset built into the clutch plates. If turned the correct way, the unit works normally. If reversed, there is additional tension, AKA friction/preload between the plates and they may act as described here.

I heard something like that too