W123 300TD non-turbo wagon/estate with manual 5, 220k miles.
Suffering from harsh vibration when putting strain on the driveline in low revs.

For example, accelerating normally in 2:nd, 3:d, 4:th gear from lower revs. Once it picks up speed and engine revs higher, vibrations go away. Also, when only pressing the accelerator very (very very!) lightly so the car barely accelerates, this is not happening. Same goes with engine braking, when the speed and revs get down to a certain point it starts vibrating badly.

Vibrations and associated noise is consistent with engine revs, so this is probably not anything past the transmission. Feels very harsh, as metal against metal.

Where to begin?
Front engine mounts? Rear one? Throw out bearing? Pilot bearing?

Could try to catch a video if it would be of help.

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Tomas, Sweden
1966 Mercedes Benz 230S with OM617.912, automatic. Disk brakes from W108
1983 Mercedes Benz 300TD grey, OM617.912 and 5-speed manual
1983 Mercedes Benz 300TD blue 7-seater, OM617.912 and 5-speed manual