The rear end of my truck is extremely stiff. When I go over a bump at all speeds (usually go over them slow), the rear end drops like a brick and everything in the bed hops around. I've got a set of Downy long AAL and a set of Rancho 99144. Is it the AAL or shocks that are causing this stiff ride? Is there anything relatively cheap to do to fix it, or am I better off getting a set of deavers or alcans with some bilsteins?