My S430 has a problem when changing gears under acceleration. If I gently accelerate, it changes gears smoothly, and likewise does so when it's cold. Once warm, what can best be described as a smooth shudder sometimes occurs when changing gears, there is no "clunk." I replaced the engine and gearbox mounts, because they needed to be done, but that didn't solve the vibration problem. I am waiting for a dipstick to arrive so I can check the auto gearbox oil levels, and quick glance of the flexdisk coupling to the tailshaft looks ok, but I haven't as yet crawled under the car and tested it by prising a screwdriver between the fastening bolts to see if there is cracking in the rubber. Does this problem sound familiar to anyone out there, or could it be a problem with the gearbox?

Richard

 

I only changed one flex disk, it was on a w140 at the transmission side. The thread and rubber are almost torn apart. I did not have vibration.

 

Check your trans fluid.

Those flex disks usually last forever. I would definitely check them since it's easy to do but most likely they aren't your problem.