i Have a 2005 2500 cummins with a 6 inch fabtech lift the vibration was there before i did the work to the front end, I did upper and lower ball joints on both sides and all new tire rod ends and a passenger side u joint and took it to get aligned. drove it still had the vibration, i rotated the tires and still the same thing, the truck drives straight and dose not pull to the left or right, The vibration occures at 50mph and continues form there on out getting a little worse at 60 but not much, I have to do shocks at all 4 corners this weekend there pretty much shot and leaking like a siv, not sure if they would cause a print end vibration or not other then getting the tires re balanced I'm at a loss any suggestions would be helpful
thanks

 

Also the the tuck carries around 2000+ pounds at all times because its a welding rich i will be installing helper bags next week to help with the weight and to bring the *** end of the truck back up to where its suppose to be it sags about 1 1/2 -2 inches in the rear due to the weight

 

I am taking a stab in the dark, and say that the shocks very well could cause a vibration,with the shocks as bad as you say they are then the spring has nothing to control rebound of the springs. Thats where I would look at. Good luck

 

Shocks can cause vibration and cupping.

Since you know the shocks are shot, sensible thing to do would be change them and see if you still have the problem.

 

true there getting changed this weekend i have some bilstein 5100s that are going on

 

whell i just figured out the cause of the vibration the drive shat u joint blew apart going down the highway i crawled under the truck to find tranny fluid pouring out and a nice crack on the tail of the transmission

 

Sorry to hear. I was going to guess driveline vibration due to possible excessive pinion angle. But I was guessing it was from the front shaft.

 

Yeah sorry to hear that. When I've lost a rear u joint, I generally feel it first at very low speeds, so I wouldn't have guessed that was your issue.