ok so i have searched on here for an hr or so and found nothing at all. Tonight while i was at work on break i was pulling my truck up closer to the door at work since im in ohio. Its snowing and blowing outside about 14 degrees right now. I was backing up and the rear end acted like it was hopping around ya know one tire going the right way and the other going the wrong way lol.. BTW i have a posi locker in the rear i have not checked the rear gear oil yet but i bought a quart of 85w-90 tonight just in case its low. Could this be the problem i mean low gear lube? I know the U Joints need replaced front and rear. So let me know what you think. Its just scary driving on snow covered roads and the rear acting like it wants to jump out from underneath the truck. Thanks in advance

 

U-Joints could cause that I think. Start at the U-Joints, and when you're under there, check the gear oil. If I recall, there is a special additive for Posi gears, so don't put regular 80w90 gear oil in there.

I found this: AMSOIL - Slip Lock® Differential Additive (ADA) It describes the additive well enough.

 

Thanks NullHead

I found out from my brother in law that he put a Detroit Posi locker in the rear and a Detroit limited slip in the front. He also told me that when it gets really cold out that the rear sometimes likes to hoop around due to the rear lube being really thick.