I have a vibration in my truck that begins right on acceleration at about 20 km.hr. I had all 3 u-joints replaced, and my drive shaft balanced. Still there. I've just put all new rotors on and that didn't make a lick of difference either. My next try is the shocks then new rear springs and if that doesn't fix it I'm going to get a set of Timbren Spring helpers.
I've been told 2 different problems with these truck.
a) The intermediate drive shaft on these units cause the drive line to shimmy no matter what you do. If you go to a 1 piece drive shaft the problem goes away.
b) Guys that have put spring assist or Air Bags on there truck that were suffering from this vibration have said that after the Air Bag or Spring Assist is installed the vibration goes away.
Sucks doesn't it....I also haven't had my tires balanced or wheels checked for trueness to see if that has anything to do with it as well...
Ev