I have a constant thumping in my 2006 2500hd with 6.6 and 2wd. extended cab. I thought it was the front wheel bearing and replaced it. It did not help. It continued to get louder and I was afraid it was a shifted belt in the tire. I replaced the front with a spare. I then moved it to the rear when that did not work. I sat in the bed today and listeneed while it was driven and it sounds to me in the drivetrain. I removed the driveshaft and the u-joints seem fine as well as the carrier bearing. I am wondering it it is a rear end problem and if there is a common failure. The rear does not seem to posess an excessive amount of slop. Interresting enough the noise does quiet...not completely when making left hand turns at a speed high enough to shift the trucks weight off of the centerline. Braking and accelleration do not aaffect the intensity of the noise in any way. The truck seems to almost lurch along with the noise now and it is felt in the floor boards.

As of now I am wondering if I need to pull the rear axle and check the bearings.
Any input would help.

Art

did you ever get this fixed?