82 300D. Driveline Vibration
 

Okay, the Vibration starts about 50mph through to 70mph. It shakes the entire car-very little if anything coming through the steering wheel.
Steps taken 1)balanced wheels twice with different machines with no difference
2)swapped all four tires from my other car with no effect
3)replaced driveshaft support and bearing with no difference
4)replaced one rear axle shaft and right rear control arm after it collapsed no change in vibration
5)replaced engine and transmission mounts
6)replaced steering damper
The left front caliper is sticking, and it could use front shocks. The tie rod ends and upper control arms and a ball joint are about a year old and still okay. The vibration is speed related-no change with engine rpm or when shifted into neutral. Smooth as can be until 50mph then, it just goes into a crazy resonance until about 70mph. The amplitude gets lower after 70mph but, it is still there.
WT$@&% should I be looking at?
Any help would be great

how is the driveshaft u-joint? are you sure the driveshaft is balanced properly?

The driveshaft ujoint was replaced - wouldn't that be evident at lower speeds during 1&2 gear accel? Went to pick up some window switches(they were wrong-it was an 87300sd not a 82300d like the ad said) and got up to about 95 mph and could feel it in the wheel a touch and some weirdness in the front end generally so I'm going to get it up on a lift tomorow and double check everything

It's good that the u-joint was replaced. They will sometimes wear sort of a notch in them due to operating in almost the same place all the time. I have cured the vibration when this has been the problem by putting a washer on the passenger side of the carrier between the carrier and the body. This causes the u joint to operate in a slightly different position. Since you've replaced the joint this is not a factor.

Are you sure that the driveshaft parts were marked before disassembly and then assembled back to the same relationship with each other? If they are not, the driveshaft loses its balance.

When you fitted the propshaft did you let the car settle on its wheels and push it backwards and forwards a bit before tightening the centre support mount and the two big nuts?

How did this problem develop? What work was done prior to the problem?

It would be useful to differentiate between a wheel vibration and a DL vibration, as their frequency will differ by a factor of 3. An axle problem might seem like DS vibration also, as the three-lobed spider in concert with a 3.07 final drive ratio will offer the same frequency as an OOB driveshaft. To possibly eliminate the axles as a problem, add weight to the trunk so that the axles are running perfectly straight and see what happens.

I'd also suspect an imbalanced rotor or hub combined with worn shocks. Good shocks will overcome a minor imbalance.

Okay here is an update-the axle I didn't replace has about an inch of movement in and out-so I guess I need to replace it. Also the r front outer tie-rod end is pooched.
I will report back after I scrounge up some more money and time. Funny that the boots aren't ripped, no leaks or noise but, like I said-an inch of travel in and out. Ugh

Thank you for all the advice so far
I'm starting to hate this car
Cheers

Hate it in to submission, but stick with it. It will get better!

How are your flex discs on the driveshaft?

Axles are supposed to have that travel, so that the axle can change length as the suspension goes up and down. Axle in/out movement is NOT your problem....

Yes, true, play should be checked by twisting/rotating the axles by hand. Easier to check with them off the car.