Fis Teck

I have a customer with an 05 Dodge bad shake or surge on a pull or on constant speed. It is the worst when he is pulling his fifthwheel. Has had the
drive line replaced under warranty helped some. Has only 6500 miles on the truck, has done this from day one. Has pulled three different trailers and they all make it do it. Pulled with no brakes hocked up and nothing in any for the tanks, surge still there. Will do it at any speed. Does it more in 38 to 70 mph. range??? With out the trailer is barely there but is still felt.

SolarExpress

Is the rear axle perpendicular to the truck frame? Are the tranny mounts broken? The motor mounts? I just throw them out to see what sticks since weight seems to magnify the problem. All three of those would be made worse with weight. Is the driveshaft straight? I had my u-joins replaced once and the tech did not center the shaft with the pinion very well. One side of the joint cap was flush with the retainer, the other side stuckout about 1/16". I took it apart and centered it and the vibration went away.