That part isnt breaking or too loose, I have started to think that it may be TOO tight. When I said that the diff spun, the axle from the stuck wheel all the way into the diff would be still (including the gear attached to the axle inside the diff) and the diff was spinning like its supposed to with the good wheel. I had the motor off, so the diff was allowed to spin freely....I'm not sure if thats any more clear
After thinking about it at work all day, I'm gonna take just the diff and the inner axles in my hands and see if there is any binding in the diff. If it's not that, then I will look harder at that joint cup. I may actually need to widen the slots in it. Cause I think the pins on the outer axle may be getting stuck in the slots in the cup...?
I'm VERY certain that nothing is broken or breaking. I had EVERYTHING in the rear apart, and it all looked good. Theres just some tiny thing that sticks when you put the whole thing back together
Just another clarification: It doesnt totally jam, like it would if the cup was like you said. It just gets slight constant resistance as it turns. Which is enough to screw a lot of stuff up when the car is this small