lunging when shifting

hey ppl. maybe someone could help me here. everytime i shift i have a lunge. ive been told pinion gear....u-joints and other things. my u-joints are solid. i dont really think its my pinion gear. i was actually stabbing in the dark w/ this next "maybe". it has the original clutch in it since it was manufactured in '89. could this have anything to do w/ it. the rearend has just the normal play when the wheel is turned back and forth while in gear so this is why i dont believe its my pinion gear.
any help here would be awesome!!!!!!

respectfully,
HellBound

actually 3rd gear does grind a wee bit but goes right in. the more i think about it. sometimes when i am coasting up say a stop sign and go to put thtranny back into first i can feel and slightly hear a clunk as in torc taking up the slack somewhere in the drive train. u-joint would be so much easier then a new rearend.

HellBound