Drive Shaft Problems?

just did a clutch job in my tacoma, 3.4l extended cab, and the clutch seems to be operating fine. Now I have a new problem, if I'm coasting along in gear or very lightly on the gas I can hear a high pitched squeaking noise coming from what sounds like the rear of the truck. Also if I'm driving up a fairly steep hill in 4th or 5th gear or whatever under a decent load the truck will start to shudder pretty bad then immediately stops when im not on the hill. I've only noticed the shuddering happen on that one hill though, although I haven't really driven on any other hills that steep recently. Does this sound like ujoints? drive shaft out of phase/balance?

I did forget to mark the flange and output of the transfer case to make sure I put it back on the exact same way, but would if it was on backwards or something would that have other symptoms?