Rear end wrapping question?

Hello, I purchased a 98 T100 4X4 with 100K miles and it has somewhat of a strange
problem. When you stop it feels like the rear end twists 20 to 30 degress. When you
let off the brakes it comes back but it feels like the whole truck moves. It obviously
can't be moving as far as it feels as it would tear the drive line apart but??
Anybody else have this type of issue? I have checked everything around the rear end
and there is no evidence of movement. Also I have just removed the rear drums and
it appears to of had a brake job not to long ago. The brake job is decent as all the
hardware is also new. Anybody out there with any ideas would be greatly appreciated.

Check to see if the rear brakes are adjusted correctly. It could be that one of the rear wheels is grabbing harder than the other. Also check to see if the torsion/sway bar links are broken/loose.