Just recently bought the truck listed in my signature....

At about 40 mph it starts to slightly vibrate and the faster I go the progressively worse the vibrations get.

Starts off I can feel a little vibration in the pedals, then the rearview mirror starts to shake, and eventually I can feel it in the seats and a bit in the steering wheel and I can see the bed vibrating in the side view mirrors. There is a little noise with the vibration as well.

It is pretty significant vibrations...but where to start the diagnosis?

I don't think it is the tires...they are pretty new and the vibration is constant once you get to 40-45mph and above...it never goes away.

I am thinking one or both driveshafts or transfercase?? What are the symptoms of a bad transfercase? I just had it in 4wd the other day and no noise or clunking....

Any ideas?

 

I purchased a 2003 2500 4X4 a couple of weeks ago. I had a similar problem, onlt mine started at 60 and got real bad at 70. I turned out to be the u-joints at the steering nuckles in the front axle. I just finished replacing them a couple of hours ago. Truck runs much smoother now. I originally thought it was the front drive shaft so I removed it. The bad vibration went away but I could still tell something wasn't right. While changing the oil I grabbed the front input yoke and "rocked" it back and forth, I then heard and audible clank coming from the u-joints, problem found.

 

Check all your u-joints.

 

Check the u-jounts, but you could have lost a weight off a tire, or have a knot come up on one. It wouldn't cost much to have them rebalanced.

 

Yes, im having a similar problem with my truck. Found 1 bad u-joint in the front and dealer put some additive in the rearend and the problem seemed to go away.