I have a 2011 S550 that was previously flood damaged. Changed and re scn coded most ECU's, repaired all wiring, no electronic errors anywhere now.

Initially transmission slipped between all gears so I had TC replaced, cleaned valve body and it cured the slipping but car shuddered. Will describe it best as possible below.

1st and 2nd gear not under much load, seems to be fine, 3rd 4th and 5th shudders, vibrates quite bad unless I drive very soft on the gas then you can hardly feel it, 6th onwards, hardly noticeable, as it changes down vibrates bad again (under transmission braking load)

So I took the plunge and changed the entire interior of the transmission, all the gears, clutch packs etc. Figured that would cure it.

Same problem WTF!!

Then my mechanic noticed the drive-shaft seemed to be vibrating towards the rear diff plus the rear diff was clicking. Thought we had finally nailed the problem, water in the diff.

Bought another diff, just had it fitted (other one did have water in it) , same problem. I am completely and totally stumped.

Please can somebody tell me what to try next. I don't think problem is transmission but I guess it could be, even though its been mostly replaced, valve body has been stripped and cleaned and is like new, immaculate. Plus star diagnostics is giving no errors on transmission at all.

If the car is driven very gently, its almost not noticeable apart from 3rd and 4th. But if you put your foot down, it vibrates and shudders very badly.

It seems (but I'm not certain) to be related to drive-shaft between transmission and rear wheels but I cannot see how.

One other point that mechanic (the guy is very nice and helpful, really trying to help me nail this down, I thinks he hates the sight of this car by now :-) ) thinks should not make a difference, when car arrived, they could not move off transporter as was stuck in park, so they disconnected the rear of propshaft to roll it off, when I re bolted it together atthe flex disc, I did not see (nor look for if I'm honest) any markings so figured orientation was not important, I did read on another forum that these are balanced at the factory, not sure if I could have bolted it together at incorrect rotation point, mechanic says this should not have any profound effect such as this, but I wanted to put it out there in case members thought it relevant. Finally I guess it could be center bearing, is there anyway to test this??

I really hope someone can help pinpoint this, I have no idea what to try next.

thanks in advance

Terry

 

SOLVED

Solved and a big thanks to Dan for sending me the Mercedes Tech Docs to help troubleshoot

Turns out it was the driveshaft, not bearing but the shaft itself. Not sure if it was something inside it but at speed and under load it started to wobble

replaced shaft, driving and gearshifts now seems perfect

 

Thanks for posting the solution. Vibration problems can be very vexing. Adding one more item to check is helpful