The aluminum ds forks on each end fit the ujoint's/snap rings perfectly with no modding. It was the steel slip yoke fork end that needed the thinning of the snap rings. They were perfectly straight and polished to a factory shine so no deviations or obstructions.

After all that, I still have the original clunk & jerk after reaching @45-50 mph & ONLY after coasting then accelerating. There is no clunk, no wobble, no jerk, no vibration, under acceleration to ANY speed from 0-100. Only after coasting and re-acceleration does it appear. The driveshaft is straight, balanced, and newly u-jointed (a word?) with brand new tires. Also, the differential and hub bearings are solid.

I searched everywhere for my exact symptom scenario but it was hard to find. This coast/accel clunk & jerk was the closest I could find with a partial exception when he says: "..the harder I hit the gas the more pronounced the jerk is....". Now, that's true with mine also, but with a more subtle feather of the accelerator pedal only. However, if I punch it, the clunk/jerk disappears completely. As a matter of fact, the lighter the feathery acceleration, the worse it is, but only at speeds above 45ish mph.

I'm 99% sure it's the mounts/bushings. Even though this thing was idle for 13+ years, it does have 127,000+ miles, the original trans mount, and torque arm inner bracket bushing from 1995. When I was under the car on my back doing the ds they both "looked" and felt ok with no super obvious disintegration but I didn't really try and torque on them with a pry bar or whatever to see how much real play there might be. Honestly, I wasn't thinking about any other solution at the time but my "new" one-piece aluminum ds and ujoints. The clunk and jerk was so profound that I wasn't even thinking bad bushings could be the problem. I'll hop under there today and do a more comprehensive assessment.

Re: mount replacement's
The poly torque arm bushing should be fine as far as potential excessive vibration issues. However, the poly tranny mount's from Energy Suspension or whomever, seems to have mixed results with vibration as well as height issues which may change the driveline specs. Also, the oem torque arm bracket has rivets to grind off if you want to sandwich a new poly one in there. A new complete inner bracket would be simpler. Thought's?

 

check for play in the differential? is this auto or manual trans. auto check for lose bolts or play at the converter/flex plate. manual, does it do it in all gears? check for excess play same as differential

 

No doubt its both bushings. Took some pics and a vid but even an 11 second vid was 24 megs on lower res setting. I'm pretty sure 2" of vertical play between tranny and support is out of acceptable limits . The problems reported by a bunch of folks with the poly replacement for the tranny is still weighing a bit on my mind. Surely, at least 2 or 3 experts here have used them?