Shaking badly

[rErnspiker]

I have a 2003 4x4, QC,SB,SO 5-speed with a bad vibrating problem mainly noticeable when loaded at take off. I have searched all the postings on here, but I haven't seen anyone with quite the same problem. When pulling my tag trailer, no matter what amount of weight is on it, my truck violently shakes. This mainly happens in reverse, but also a little bit in 1st and second. This is my third Cummins, and I wouldn't trade it for anything, but at times it seems as though the truck is gonna shake apart. This has been a problem since new, it now has 27,000 miles on it, the dealer has taken the clutch out and had it pressure tested, it tested fine. Does anyone out there have any suggestions on what could be the problem? The dealer is currently contacting his rep. about it. Does anyone else have this same problem?