You are going to have to pop the cover off the rear diff and send us a few picture.

I'm thinking the pinion to ring alignment off because of a bad bearing or not set up properly.
Can you move the input to the diff up and down or left to right?

Usually a spun hub won't lock up the diff.

 

You are going to have to pop the cover off the rear diff and send us a few picture.

I'm thinking the pinion to ring alignment off because of a bad bearing or not set up properly.
Can you move the input to the diff up and down or left to right?

Usually a spun hub won't lock up the diff.

I don't know what other pictures you'd want.

 

See post 10 in here???

Rear Drive Shaft not spinning...

Well as I bring this Cj7 back to life, found another new problem... I was driving the Cj in the neighborhood had a little noise at the start of a hill. I took the hill slowly and made it. As I pulled into my driveway, I switched gears and the jeep did not respond. No matter which gear I...

www.jeepforum.com

When doing this test, the wheels have to be on the ground!

-------JEEPFELLER

 

Sounds like maybe the clutch is slipping

 

I would pop the brake drums off and try rotating again.
If the diff turns then you have found your problem.If not drop the driveline and try again.
If it turns then you know the issue is in the drivetrain.
If not then the issue is in the diff itself.

 

Looks good in there,
I agree with jeepdaddy Try taking the drums off. Watch out for falling brake shoes...

 

Have you disconnected the drive shaft? By chance did You changer the gears in just one Diff ?

 

Thank you guys for all of your help! It was the brakes. Luckily no falling shoes. I was able to get it home under it's own power. Which brings me to a new thread. I can't get it past 40 mph. It happened kind of suddenly, first idling rough and stalling then having a hard time accelerating to shift speed and it would jump and lurch forward until it would gun itself so I could shift. It will only do this from 2nd to 3rd and 3rd to 4th then I'm stuck at around 40 mph Iwill start a new thread with this information. Thanks again!