Noise like U-Joints?

[spspspspoon]

65 350 3ott short box 3.73 rear

the noise sounds almost like a loose u-joint
at highway speed it sounds with too little throttle or too much.. as if the engine isnt pulling or pushing the wheels..and the space in between isnt tight

Also have Maybe the same origin of noise when I'm slowing down Without trans in gear.
again like it is slightly off one way or the other from each other
like a bad u-joint...

I've wiggled the drive shaft as checking the u-joint
and seems like the yoke going Into the trans maybe loose??