Ive been trying different things with little success - pulled the shaft again and taking it back to the shop to have them verify its balanced/straight.
I did check the rubber support, I can push the tailshaft yoke up about 1/4" but its rock solid when pulling down. Also rock solid when pushing towards pass side but can pull it towards drivers side 1/4". Is it shot? The one that was originally on the car when I got it 10 years ago would literally flop up about an inch and only clunked under hard acceleration haha.
This one was fine right up until I noticed this slight vibration so maybe it was both U joint and it dying. It was a used one I bought off Rick years ago.
Now when I changed it years ago I cant remember the safest/easiest procedure on how to do it... Any tips? I thought I put it on jackstands on the axle tubes, put a jack under the support, took bolts off the bottom of the car and slowly lower via jack then remove the 4 19mm bolts holding it to the punkin...
So the plan as of now: have driveline shop recheck balance/alignment if good then replace tail shaft extension with junkyard one and try again...