My wifes 2009 6.7L cummins started to vibrate the other day. It starts when you get up to speed and doesnt quit till under 5mph. But as you slow down it feels like your driving on washboard and then quits. We can hear it, feel it in the floorboard and in the steering wheel. Any idea's? The mechanics at my local dodge service dept are claiming the tires are causing it, but the truck doesnt have 38" super swampers on it. The tires are 33" nitto terra grapplers AT. I had the tires balanced, rotated, and aligned, with no joy on the problem. I really need help on this one.

 

Could be anything from bad U joints on the driveshafts to imbalanced tires. Rotate the tires around and see if it changes. If not, move to the driveline.

 

Thats kinda what i was thinking, a bad u joint. The tires have been balanced and rotated, still no joy. The mechs are slaving on a different set of tires to see if that changes anything. Im giving it a 10% chance thats the problem. The tires are brand new, around 2000 miles on them.

 

Had similar vibrations in my Jeep CG. Turned out to be the 8 1/2" lift was causing excessive angle in my rear driveshaft. Had to replace the transfer case with a short slip yoke eliminator, but it solved the problem. Is your truck lifted? If not, probably a bad U joint or you may have dinged the DS and put it out of alignment.

 

No lift, havent been off road, just pavement. Just the wife too and from work truck.

 

Check the rear driveshaft carrier bearing