When driving the 06 megacab I noticed a little vibration during a slow start. I can only describe it as 5 slightly small vibes that I can feel in the lower back of the seat, every slow launch this vibe can be recreated. If you put your foot into it you will not feel that vibe, nor will you feel it ever again anywhere on the speedo.(I have not towed with it yet, have not had time to add brake controller.)
The dealer has replaced the rear driveshaft, and rebalanced the stock michelins(they were a bit out), the problem still exists. The dealer has acknowledged that the problem still exists, and I am sure they don't even want to entertain the thought of this problem being the stock TC.
Anyhow, I guess these are my questions.

What could be causing this vibe? do any other megas cabs out there feel that same vibe?

 

i have the same thing in mine i'm not sure what it is ? the hanger berring in the drive shaft but

 

Mine has it but is getting less noticeable as the miles add up. Some say it is the carrier bearing that needs to be shimmed down, I think it may be the rear end gears breaking in. I'm no mechanic, but they say to take it easy for 500 miles to let the diff wear in right. The following is from a Dodge service foreman.
http://carsondodge.com/forums/showthread.php?t=37

 

Thanks for the help, good link.

 

If it's what I think it is, the problem has been around for a while. It supposedly relates to improper pinion angle (the angle between the pinion shaft and the driveshaft, which is the angle that the rear ujoint operates under) This can be fairly easily fixed by putting wedge-shaped shims between the leaf spring and the spring pad on the rearend. The aim is to cause the pinion to face slightly more up, thereby reducing the angle on the ujoint. I think the reason you only get it on soft takeoff is a harder takeoff causes the rearend housing to rotate slightly rearward due to natural torque reaction. This is the same phenomena that traction bars were made to limit and harness. The direction the housing rotates in raises the pinion, which reduces the pinion angle. This eliminates the shudder caused by the jerkily-rotating ujoint, since reducing the angle of the joint smooths rotation of the joint.

At higher speeds, the jerkiness might still be there, but would be so rapid as to not be noticeable. As you might imagine, a ujoint operating under these conditions will last longer if the severity of the angle is lessened. You don't want to just put it at 0 degrees (no angle), as the housing will then put a negative angle on it when rotating rearward under acceleration or towing.