Ghost Vibration... Torque Converter or Rear Diff bearings or?? Please help!
 

2007 E550 4MATIC with the 5spd (722.677 06 606183) 150K miles --- with an intermittent but severe vibration issue on highway that only occurs after driving at set speed for awhile. Very unlike any typical wheel/axle/tire/shimmy issue.... this issue is intermittent and non existent in the city or when driving with varying speeds. The car has new tires, alignment and has had the flex disc checked and other mounts as well. Have also gone over typical checks.

Is there a way to single out the Torque Converter or the rear bearings while driving to single out or cross items off the list? It occurs when cruising for a good while (which is why mechanics can't replicate) and is a sonic boom sound and shake vibration that starts off quieter but quickly ramps up and gets louder and more seemingly violent. It seems to come from rear end but literally sounds like a helicopter is landing on the car. Thought it may be the rear differential and the rear diff fluid was just changed but didn't help/fix. When this occurs and having to slow/pull off the highway and stopping the car, there is no evidence of any issue and the car pulls away from a stop and drives normally as if nothing happened. Until it randomly happens again. No check engine lights or transmission lights. No issues with in town driving (non highway).

Mechanic is guessing that it could be the rear diff bearings OR torque converter due to pressure seals -- which could be a bad conductor plate and/or requiring a new TQ or transmission.

Any help/advice on things to try to single out the issue would be greatly appreciated before we keep fixing things that are not fixing it!!

I was thinking the flex disc as well but mechanic says it was good. We also discussed the rear diff bearings going out and there have been some posts that sound like it could be but of course there are no codes for either of these issues and do not want to fix things are aren't broken.

Question -- are there any steps that I can do when driving the car that will rule out some of these issues? The last time it happened while driving 75 mph I put the car in neutral and the vibration/sound did not change -- so I was thinking that it might not be a torque converter issue but I'm not a transmission expert nor know if everything "disengaged" when i shifted out of gear and back in (while coasting to a stop).

Any other things that I can do to single or cross things off the list would be greatly appreciated. Again, when this occurs it is a very loud booming and rotational vibration.... fairly violent, not just a shimmy. Come to a stop, and it's gone. Car drives away fine as if nothing happened.

Try Changing Your Rear Tranny Mount, See MBWorld Link Below
 

https://mbworld.org/forums/s55-amg-s65-amg-s63-amg-w220-w221/444981-transmission-mount-replaced.html

CV axle? I've had one that was only barely noticeably loose on the inboard end (closest to the differential). It made the car vibrate only when it felt like it, and that wasn't that often. Changed out the axles, all was well.

Cardan flex disc

I experienced something like what you describe and posted in another forum about it.

My vibration has never returned after my repair, although I cannot say I am thoroughly convinced that what they replaced was the source of the problem. Still, several thousand miles later, all is okay.

https://www.benzworld.org/forums/w21...th-wobble.html

Check these 2 links out. I'm going to put my 2011 in the shop to check it out. If it is torque converter my extended should cover the cost.

https://mbworld.org/forums/e-class-w...shudder-2.html

You Tube

Driveshaft middle bearing?
Lots of mass there that may produce weird sounds varying with the shaft's rpm.

Unlikely that its the driveshaft in my case. I have been under the car and inspected shaft from the trans to the rear. Everything looked and felt good. Took it to the dealership when it first started and they said it was the motor mounts, but this doent make sense as i dont have any rough idle.

Hi E5504matico did you ever get your problem figured out? I have a 2014 E550 and have similar issues without the loud bang. A mechanic mentioned Torque Converter possibly? Let me know I would appreciate it!