Ok so i know NOTHING about rear ends except that I have an 9 inch in my 65,8.8 in my gt and, 7.5 in my 88.
But anyways I decided to be a dumbass and did like donuts on saturday night and when i launched afterwards i heard a LOUD crack from the rear end...I stopped right up the road and took a look to see if anything was broken...didnt notice anything outta the ordinary. got back in it and took it easy everytime i get above 70 the car starts swaying like in the rear....and if i leave hard it feels to pull to one side...I dont know weither I broke something internally can anyone help me figure out what i did?

 

Sounds more like you broke something in the rear suspention not the differentail.

 

like what?

 

I am not sure what exactly happened but I had a simular problem with my truck, after reaching about 70 mph it would start to sway, I jacked up the truck and sure enough the ubolts holding the differentail to the leaf springs had come lose. I would just jack the car up on jack stands supported by the frame of the car not the rear end, then see if you can move the rear end side to side or front to back.

Granted your car is not the same as the truck was they theory and symptom are the same

 

Well I know my Ujoints prolly are shot but is that whats causing the problems, the bolts are tight.

 

Tight bolts on bad u-joints arentgoing to do anything to keep them together. And when they go you better hope it isnt the front one. As for the rear sway, maybe broken sway bar, maybe control arm or control arm bushings. Or you tore a torque box loose.

 

I took it for another ride and i went around a turn around 40 and i heard a loud crack and it thumped on and off coming back.....now im worried

 

Jack up the rear and check the control arms. Sounds like you may have broken one. Now you see why the NASCAR mechanics hate it when the drivers do donuts after winning a race.

 

Update...I jacked the car up, and nothing!! i cant see anything wrong except i found out that my parking brake was f***ed up. But as for the rear end nothing seems to be broken, loose, nothing you think its internal?

 

Did you check the shocks and mounts?