ok guys i had a feeling something wasnt right with my rear end when i blew through a rear u-joint in the first 6 hours of owning my truck (96 F250 HD lifted) so i replaced the joint and had a friend move the truck forward in my driveway and the whole rear diff moves upwards untill the driveshaft hits the two clamps holding the u-joint into the rear diff. same when you reverse. what would cause this? the only thing i can thing of is the two shocks that attach to the frame and rear diff on the inside of the leafsprings are no good but i really have no idea.

 

Axle wind-up (rolling) is normal but not that much, something is loose or missing. It's not the shocks IMO. The axle shouldn't do that even with the shocks removed.
The leaf springs are the only thing that stops the axle from rolling. See if they are fastened to the truck and axle housing.
There is supposed to be a few clamps holding the leaves together too. If they are broken or missing the the axle will roll more than normal. The rear spring hanger brackets riveted to the frame are prone to rotting through too.

 

alright i had a look around and all the rivets on the rear spring hanger are seated fine no problems there. there are clamps on the leafs where they are supposed to be, the only thing wrong is that i am missing the front half of a leaf on the drivers side.

its the 2nd one up in the bundle and it broke right in the middle of the leaf.

could missing just half of one leafspring on the one side cause axel wind-up to be that bad?

 

Yep, especially with a lift. How much lift do you have?
Is you center bearing shimmed?

 

x2--I put a lift on and 5,000 miles later blew a u-joint and burnt up the carrier bearing. Is the rear all spring or is it blocked lifted?