Sounds like you have a lot of slop somewhere. If it,s not in the drive shaft pull the rear cover off the diff. One wheel should not turn more than an in. or 2 before the other wheel turns in the opposite direction. There should be no up or down motion inthe pinion flange & only about 1/8 to 1/4 in. turning free play. The carrier that the ring gear rides on should not have any side to side movement no more than .012 in free play. Examine the spider gears & shaft.
