When i let off the acelerator im getting a vibration and it feels like its coming from under the truck. When i acelerate i dont feel it. I'm thinking bad U-Joints.
I have a 2004 4x4 dodge cummins 6spd 93,000miles

 

I was also thinking u-joints.

 

Jack up a rear wheel, the while looking at the joints, have someone run the wheel back and forth by hand.

 

Pinion bearing or loose yoke...Its vibrating when running on the coast side of the ring...

 

Could also be the driveshaft carrier bearing if it has one, they will vibrate on decel usually.

 

X2 on the pinion bearings. Check the u-joints pull the shaft and see if they are binding up and while its out check for play in the Pinion and jack the rear axle off the ground and spin the tires see if it sounds rough or anything.

 

Another way to find a bad u-joint is to touch them. If one it hotter then their you go.

 

Thanks for all the good info fellas I had two bad U joints. one was binded and the other was loose.

 

I reckon you installed greaseable joints??

 

Check your front driveshaft going into the diff. Kinda felt it more when I let off too. I posted it in theis section, "weird vibration" check out my post, I hope it helps.