99% sure the diff is blown but is there any way to check without taking the diff out and taking the housing off? I have the car up on jackstands right now. Thanks!

 

I'm pretty sure if it's fubared you would have noticed it while driving.
check the fluid for metal chunks too

 

Try spinning the driveshaft with your hand and see what the wheels do??

 

Yeah, when mine went, it completely grenaded and I had to have it towed to the shop.

Before it went though, it began to make a lot of noise. It sounded like grinding and it always occured at the same rpm and the noise always had the same pattern, like clockwork.