The problem I am having is that while driving there will be a random clunking noise coming from beneath around the middle area . I can't really pinpoint to just accelerating or decelerating because it does it during both while driving straight.

I put it up on Jack Stands to try to simulate it and nothing , but soon as I put it back down and drive the clunking comes back.

I'm thinking it could possibly be the u-joint but am not sure

Also should the yoke on the transmission (the silver shaft that comes out the back of the tranny to connect to the u-joint and driveshaft) have any play in it because it does it doesn't leak any fluid out of it so I don't know???

Does anyone know what this could be

Oh yeah and its a 350 connected to a turbo 350 Trans.

Thanks