I have a 1990 3/4 ton chev pickup with an automatic transmission, 206,000 miles.It got a new transmission about 3 years ago. The rear end makes a loud clunk when I shift in and out of gear and their is some visable slop,(the drive shaft goes from 2:00 to 4:00 when I shift from forward to reverse with the parking brake on). Does anybody know if this means I need a new transaxle?
No, it sounds like you need to have the universal joints on the drive shaft checked and replaced. If one breaks, you will lose your drive shaft so don’t wait.
If this is a 4x4 check the front CV-joints and U-joints too.
Once you rule out the play is not in the U-joint, and that the pinion shaft is tight (no back and forth slop) then it’s the ring and pinion gear showing it’s age. The differential can be torn down and the clearances adjusted, a tricky and expensive project best left to experts. It would be cheaper to install a low-mileage axle (the whole thing) from a salvage vehicle. Be sure to maintain the same gear ratio. Or you could nurse it along, change the gear oil and add a can of STP to take some of the slop out. They seldom fail catastrophically.