[West Coast GTO]

Last year replaced the driveshaft after installing a used short TH400 tailshaft and paid a mechanic to remove old long tailshaft for the shorter unit. I still have a vibration ( although not as bad). Also, changed out the rear differential fluids and refilled with proper lube and additive( posi 10 bolt).
Just raised the car onto jack stands and noted this:
1. Small side to side movement at rear driveshaft yoke at u-joint( pressed side, not bolted side.
2. Definite side to side and up and down movement at rear trans yoke to driveshaft junction. Enough that I can slightly see the rear yoke seal move. I don't own a gauge that would allow me to test movement.
3. I can grab the rear tire and move the wheel forward/ backward approximately 3/8" to 1/2" before gear engages. I don't know if this is correct tolerance or very sloppy.
Any suggestions would help.