Vibration on deceleration/acceleration
 

2007 6.7 litre 2500 auto trans., 92000 kms. Driving down the highway, let foot off the throttle and I can feel and hear a heavy vibration - almost like the sound of the exhaust break but heavier. When the truck is idling you can't hear the noise. I can feel it in the seat and the steering wheel. Sometimes I feel it when accelerating, but mostly when decelerating. I checked my tires for wear and they're fine. Also checked the hubs to see if they were getting warm and they are fine. Checked the driveshaft to see if it was loose, but it's okay. Got the oil changed two weeks ago and the bracket recall fixed and that's when I first noticed it. Any ideas on what it might be? The truck has seen mostly highway miles and have not hauled anything yet. Thanks.

at 98,300 kms' on the 05, the center u-joint had one dry journal, and the steady bearing was shot. this is in an automatic / 4wd truck.

Just something to check. The u-joints felt good, until I took it apart.