i kept hearing a click sound when i drove my 85 2wd 4speed and thought it was a bad u joint. i jacked up the car today and noticed it didnt have any play on the you joint. so as i spun the drive shaft i noticed that the right rear tire spins and the left tire barely moves and i could hear the noise coming from inside the differential. would i have to change the rear left axle shaft?

 

It called an open differential. That is normal for a non-locked diff.

If you hear a click in there, you might have a ring gear that is chipped.

 

when i drive my truck recently the rear of the truck sways to the right when i accelerate and sways to the left when i ease off the gas i know that isnt normal.

 

if your spinning one side tire and both are off the ground both tires should spin almost equally but the other side is gonna spin backwards from the way your hand turning the other. Same with turning the driveshaft one tire is gonna spin forward while the other is gonna spin backward.

Sounds like you might have a spline missing off the other side axle shaft.

 

dunno if you typed this wrong, but this isnt true.
with an open diff (with no seized brakes) with everything in the air, sping the dshaft both tires will spin in the same direction.

check if your brakes are not releasing, and that your axle locator bolts on the leafs are intact

 

yup your right, now that you mention it. Spinning the D-shaft is the same whether it be on the ground or not. I still stand by my broke axle spline though and possibly just that sides spider gears ???? But even then you toast an axle spline you most likely toasted the whole diff anyway.