i took my front drive shaft off my 99 wj to do the outer pinion seal on the front diff. i drove it around to make sure it was not leaking anymore with out the drive shaft in. when i put the drive shaft in it was vibrating like crazy at any speed. i pulled it back off and no vibration. WHats the Problem???

Needs to be balanced.

shouldnt it just bolt right back on

Yes, I guess I assumed you had it bolted in place properly already. Make suure the u-joints are properly seated in their respective yokes.

i forgot to make a mark when i took it out so how would i be able to put it in properly????