Greetings everybody,

I am new to the forum and I would appreciate some help with a problem I have with my 1995 W129 SL320 (abt 100,000 miles).

Last week I had the catalytic converter and the muffler changed - all was done in official MB dealer.

Since then, whenever I start the car, lock the gear in 'D' to drive away, engine idling and I am still on the brakes, I feel a vibration / buzzing, which goes away after I rev up and drive away.

The vibr / buzz is bit embarassing so after I drive away from the house and I stop at the 1st/2nd red traffic light (while engine is still cold) I prefer to shift in 'N' (no vibration then) and wait for the green light, than to feel the uncomfortable vibration. After the engine is warmed up (2-3 miles driving) - no unpleasant sounds, etc - all is normal.

Above symptoms disappear when:

-the car is either warmed up (no problem when idling in 'D' plus brakes) -or-
-when although still cold, the revs exceed abt 1200.

This happens only in 'D' position and not in 'P' or 'N', 'R' (as one would expect) - and only when the car is cold.

Any ideas please?

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