I have a 03 3500 longbox with 6speed. Single rear tires 4X4.138,000 kms. I was comming back from the lake last night and when I slowed from highway speed to turn onto a side road the vibration started and it felt like the box was going to come off. I looked for loose wheel as well as running along while I looked, but could not see a thing. I got home (6Miles) and put it up on jack stands, at about 20 kph the vibration starts and the center bearing is going all over the place. The vibration becomes worse when you decelerate but is still there when you accelerate. I think that the bearing may be the problem, any other ideas? When I move the shaft by hand the rubber moves very easily (about 1/8" in any direction) I don't know if this is normal or not, all other center bearings that I remember did not move with just hand force. Thanks

 

I bet that the bearing is bad. An eighth is alot of play.