So I get this Black 85 Burban with far too many miles on it and a truck load (hee hee) of work to do. 1. I love the truck, I don't love the vibration at 55 mph! (also, When I JUST synchronize engine speed with road speed, there's a loose rattle kinda like a U-joint) I know it's not the U-joints(new and clean), I know it's not the alignment (new ball joints, Wheel barings), I dont think there are any weights missing from the prop shaft, and I think the shaft is streight. 2. I love the truck, I dont love the shudder at part/full bore take off from stop! I thought that this was a symptom of messed U-joints, but that's not it. Maybe rear gear (Ten Bolt 8 1/2")? Maybe The Trans(TH 700 R4)? I was told that a cracked flex plate could do these things to a poor half-ton truck like mine. Please HELP!!! I dont wanna kill my baby.