My car 92 500sel also shakes at around 2000rpms in either drive or neutral. PO had tranny rebuilt and they didn't do it right. There is whining nouse from tranny on idle and that shake and vibration around 2000rpm. My tranny is similar to c280 tranny, should be same family. Please let me know if you find the cause of your shake and I will be unbolting the torquw converter from flywheel hopefully next week and will run the engine to see if vibration goes away. I will report back. Good luck

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1999 ML430 Silver 135k ml
Smoked LED taillights, Alpine in-dash DVD player, 12" sub, Pioneer components, 2 amps, 4200k HIDs, ML55 headlights, 20" rims, mirror LED blinkers

SOLD. 1996 E320 145k ml. Burgundy

SOLD but miss it everyday 1992 500sel Black
Chime buzzer mod,Alpine CD/MP3 player with stock amp,Euro headlights,S600 grill,20" rims, BEST CAR EVER!

SOLD. 1990 300E White
187k ml,smoked tails,Euro headlights,17rims,Intake,12" sub in first aid kit,alarm/autostart,buzzer mod