Just bought a roller frame for a 74, BB 4 speed car.
The frame is in excellent shape, but I want to confirm that the rear end is good, as well as confirm the gear ratio...
The seller said he thought it was a 3.55, which is what I would prefer for my build.
Okay...
I jacked up the back of the frame to get both wheels off the ground..
I was surprised to find when the wheels were spun, the half shafts didn't spin...
Then I realized there were some parts missing, like the rotors, and the wheels were mounted to the spindles...
But the outer half shaft U-joints are attached to the wheel yoke...strange...
Anyway...I am not concerned about the wheel hub assemblies since I have new trailing arms coming from Van Steel...
So I put tape on the input yoke and on the passenger side output yoke.
I spun the input yoke 1-3/4 turns and the passenger side output yoke turned 1 full turn...
The drivers side yoke didn't spin at all.
Both tires are flat, so the wheels are way out of balance.
So can someone knowledgeable tell me what is going on with this rear end?
Is the internal clutch shot? Is this worth rebuilding or am I better off finding a different differential?

I have a lot of experience with engine building and restorations, but the differentials and transmissions have always been my weak area of knowledge best left for others......
Any help would be greatly appreciated...

 

You won't know if it's worth rebuilding until you open it up and take a look at the posi case. If the posi is stock, with springs, then you should see both wheels move- unless the springs are worn or the diff is broken.

 

I was able to spend some more time with it today. And found the solution...
The drivers side emergency brake shoes were locked up, preventing the diff output yoke from turning.
I was able to free up the shoes and remove the half shafts.
Did the rotation test again and the rear end acts like a normal posi. (Both outputs spin the same direction)
Also, it turns out the seller was right...It is a 3.55 gear...
Today was a good day...

 

Don’t forget, that you put the rear in bind when you jack up the car and let the rear wheels hang without supporting the trailing arms.