Check your motor mounts, transmission mount, ujoints, and rear pinion. Probably all of them are worn out. The motor and Trans mounts are not expensive to replace, just a little challenging on the motor mounts. Likewise the Ujoints are cheap and easy to replace, especially if you have a vice. if not then get a ujoint tool from autozone or some place similar. They usually have loaners. As far as the rear pinion goes. It might be able to be tightened some, but chances are if it's got a lot of miles on it then it needs a bearing replacement, which means you will have to do the third member as well... It might be something a mechanic might not charge too much for if all it really needs is the pinion bearing, but chances are it will need the side bearings on the diff as well. If your truck has a two piece drive shaft also the middle coupler or whatever it's called (carrier bearing I think?) might need replacement.