when i get on my gas lightly my truck starts shaking in the rear end up to about 10-15 (first gear) or so then it goes away then in second gear and so on it dont shake does anyone have a idea on what it could be

 

Sounds like wheel issue,maybe a bent rim.

 

No I would amagin that a wheel issue wouldn't just go away after speeding up, i think it would go away when you are at slower speeds. Do you feel it in your butt, your steering wheel or on the floor? Or is the whole truck shaking??

 

sounds like it is a front end problem tie rod ends, ball joints, idler arm, ect or a blown belt in a tire......but it could also be a u-joint. on an outside chance it could be a bad motor or tranny mount too.