I always thought that when gears went in and the car didn't move it was the clutch...in this case I change the clutch flyywheel throw out bearing and slave cylinder and my transmission still wont pull my car when it gear and it sounds like rattling inside the tanny..most likely broken right? And need it replaced?

 

diff or final drive is most likely blown.

 

Is it a bitch to change?

 

The tranny? As transmission replacements go no, it's not bad.

 

Is an axle popping out of the differential? How wide are the gaps between the CV joint and differential?