i recently acquired a yamaha timberwolf from a family member. it had no rear end. so i looked on ebay and found a differential off of a running bike. i have installed differential and then installed an axle that i bought. when i go about tightening the castle nuts on the ends with a ratchet, i can feel splines jumping and axle turns (i made sure it was on gear to lock up drive shaft). what could be the cause of this. by the way, differential does not have oil yet. i just don't wanna put tires and rims on and it no work or damage parts. any help is appreciated. thanks