From what I've read on this forum, The thumping and transmitting every bump in the road do indicate malfunctioning self leveling system.

Three things to check:
1] You might still have air in the system. There's a bleeder on the level controller (passenger side near rear axel where all hydraulic lines feed into).

2] Level controller has linkage connector to the sway bar. Sometimes the clamp on the sway bar comes loose.

3] Hose from pump to reservoir goes bad.

Bob
PS Hope you have better luck than I'm having with mine. I had accumulators replaced, now it just stays up and manually moving the self adjuster doesn't change height.

Good threads to reference are:
http://www.peachparts.com/shopforum/showthread.php?t=48451&highlight=Hydramatic+suspension+education

http://www.peachparts.com/shopforum/showthread.php?t=85061&highlight=Hydramatic+suspension+education