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?

 

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?

 

Best thing you can do is get a BMR torque arm and relocation bracket.
I have that and poly engine and trans mounts,it's rock solid.

 

I wish! God is that clean underneath. I just have a crappy little 3.4 however that prolly won't ever go past 75mph so that upgrade is not really necessary.

The poly bushing upgrade makes sense though for posterity. So, I shouldn't worry about the poly tranny mount driveline angles? I've seen some complaints of the mounts height difference being an issue and a potentially excessive vibration because of a more solid mount, no?

 

just replace the torque arm bushing with stock. I had issues with vibration when I tried poly. not everyone does. not to expensive an if its not the issue you still need to replace.

 

Ok, thanks. Should I stick with stock on trans mount also?

 

Should be fine for a V6 cruiser.

 

Your car will be fine with stock parts since it's a stock V6 cruiser.
Mine is putting down some power,everything under it is race suspension K-member on back.
Subframe connectors Strano lowering springs and sway bars,Koni shocks etc.
I went with poly mounts since it's a six speed stick and gets run hard,it has an LS7 clutch on a RAM aluminum flywheel so when I let her rip it's taking a pounding.
It's not a good daily driver,big cam highway gears not town friendly, but it's a blast to drive on the back roads out in the country where I live.
She's in the garage most of the time,never driven in the rain just a sunny day weekend fun car.

 

Got it, cheers.

 

Well, the trans mount was complete toast. The inner bracket feels tight and looks fine, as you can see, so I didn't replace it (yet). Unfortunately, I still have the original vibration but with a slighter clunky sound/feel after reaching @45-50 mph & ONLY after coasting then accelerating. It is less pronounced than b4.

What exactly does the torque arm inner bracket "feel" like when its getting worn or shot completely? That smaller end of the torque arm just looks like it sits lazily in the inner bracket rubber bushing assembly. I assume the rubber bushing keeps the arm from excessive lateral movement but how exactly does it prevent fore/aft movement? It's really such a relatively "free travel" type bushing that's simply sandwiches the tiny end-piece of the torque arm but not with any serious compression, especially not enough to prevent for/aft travel.

Finally, is there ANY other thing that could cause my very specific symptoms? I assume an unbalanced driveshaft would get worse with acceleration.