I had a vibration at various speeds. After new U joints, carrier bearing, new outer wheel, tired balanced and trued, the problem went away when I changed to a 1 piece driveshaft. thanks for the recommendation. 2008 Chevy 3500.My 01 crew cab short bed did this on heavy accelerating from a dead stop. I had a 2 piece drive shaft and this was the cause for me. I had it replaced to a one piece and that solved the problem. the truck drives like a whole different truck now. Extmely smooth and no shudder at any speed. if you have a 2 piece, get a one piece, you will be glad you did.