i have something like positive left 8.1 and right 8.4 caster on a 96 with a 4.5 inch lift. i head that somewhere the goal is 5 or 6? i know to up the caster with shims but how do i lower the caster? or atleast make it less degree? i have DW at high speed when i hit bumps and RE instructions say it could be caused by high caster. i also have a loose track bar untill the mail man comes with my new adjustable one.

 

You either need the correct lower and upper links for your lift or adjustable links. If I read you correctly your axle is tipped forward? If so, it needs to be tipped back. But it should work OK with 8* negative castor. If you have a loose track bar bushing then fix that first.