Mopar Diff Guru Wanted

[cycledog]

I have a Mopar 8.75. When I was putting on the wheels and tires as I am beginning to do my mock up I turned the left wheel as I was tightening the lug nuts and noticed that the right wheel did not turn. Unless I have completely lost my mind I thought that the opposite wheel was supposed to turn. Opposite direction for non posi, same direction for posi.

Then I turned the pinion and the right wheel turned, the left wheel turn less than one rotation and stopped turning. I am thinking I have a defective diff.

Of course I never checked it out before it was installed, note to self.

Now I know that all of the drop outs will interchange but not all of the ring and pinions will. I have a 66 A100 van, those have 8.75s and should be a 3.90 Posi, although I haven't checked. I do know the A body 8.75s are hard to come by and desireable.

The question is: are the axel splines the same? The rear end in the roadster came out of a 64 or 65 Coronet, so the axel lengths themselves are different.

Thanks for the help.

 

[440shorty]

may be ok

It sounds like your differential is open. That means that if the pinion is free (no driveshaft, or transmission in neutral) then it is possible to turn one wheel and the other wheel not turn, in which case the pinion yoke should be turning, or turn the pinion and only have one wheel turn. If the pinion is locked (auto trans in park, or manual trans in gear), then the other wheel should turn in the opposite direction.

I suspect that the differential is ok , but your brakes are dragging. Easiest way to tell is pull both drums, then try turning the axles - see if the left one turns free then.

Let us know what you find!

440shorty

P.S. The axles splines are all the same, assuming stock stuff. I've changed pumpkins in the parking lot before.

 

[cycledog]

Thanks 440,
You are correct the diff is open...another case of brain cramp for me.

 

[ronnysplymouth]

http://www.moparts.com/Tech/Archive/axle/21.html