Will Hunt

I just replaced the motor and trans mounts on a 08 s550 4matic and i'm still getting vibrations at idle (worse when in gear) and I can also feel when the transmission when shifting from park to drive or reverse. At 20-30 I feel a shudder even when in neutral and sometimes jerky shifts. Could it be the torque converter or something with 4matic?

Arrie

If you feel the vibration when car is not moving it kind of rules out the transmission as the problem, 4Matic or not, excluding the Torque Converter.

When driving the TC should lock up, which rules out the TC as a problem if the lock holds. You should get a scanner that shows the speeds on the engine and TC turbine to see if the lock holds. If it does, then the vibration source would be your engine and not transmission problem at all.

BOTUS

your first sentence above leaves it open ended as to whether or not you are saying the TC is a problem.

they are a frequent failure point on Mercedes, old fluid and or coolant leak kills them slightly faster than the designers managed all on their own

Arrie

My first sentence says car not moving rules out the transmission but not the TC, which also is part of the transmission.
The second sentence rules out TC if the lock in it works when car is moving.