2001 GMC sierra 1500 4x4 vibration in floor when acceleratin

[shackleferd33]

I have a 2001 GMC sierra 1500 4x4 5.3l when accelerating there is a vibration that I can feel in the floor. Does not make vibration on de-acceleration. also does this when accelerating while turning. I thought it was coming from the front end but everything is tight so I am wondering if it is something in the rear end and is sending vibrations through the drive shaft where I can feel it in the floor. Any comments or advice would be appreciated thank you.

[carriedi]

I would check for a bad u-joint first.