Suspension shudder on Burban

[Blackhawkdc]

Ok, hopefully some of you will have experienced this too. Got a '99 Suburban here, old body style. Factory GoodferYear tires replaced at about 15,000 with Michilin LT 10-ply tires. Replaced stock "caddie-like" shocks with real truck shocks. Got rid of the "caddie-float". The truck now has a shudder when you hit a bump. Feels like the suspension dampening is messed up. Have any of you experienced this problem on a like-aged Suburban? any ideas to remidy this without loosing the sturdy truck ride and going back to the loose floaty ride? We're gonna try dropping the air pressure in the tires and see if that helps. any other ideas? We already tried another set of new shocks. First set were the Gabriel VST's, second set is Heckethorn Nytro 9000's. So I doubt its the shocks.

Thanks in advace for any and all help/tips.

Happy Truckin and God bless,

Seth