i just pull a open rear axle with disc out of 84 trans am and i dont know anything about gears and axles. my question is the yolk suppose to spin without the axles turning? i can turn my yolk and the two axle turn, but if i put the slightest pressure on the disc, they stop turning and i can still spin the yolk. is this nomal or is the rear end bad? any insight to my unknowing of differentials would be appreciated.

 

If you can stop BOTH rotors and the yoke still turns, the rear is no good (broken ring/pinion or spider gears.) If you can stop ONE rotor and still turn the yoke, that's normal.