1994 s-10 4x4 Vibrations in drive train

I have a 94 s-10 with 4.3 vortec. It has 332000kms on it, still runs like a top. There is, however, a vibration while accelerating, the more throttle you give the more you notice it. It also increases if I add weight to the bed of the truck. I have heard from others that this is a common problem for this year and make of truck. It has something to do with the angle of the drive train and that it is nothing to be concerned about. I am wondering if this is true or should I start shoipping for a new trannie?