My 90 w124 300d 2.5 turbo has this issue with the transmission: when in reverse it feels like the ebrake is on or there is a lot of resistance. No slipping, but requires a bit of throttle to move and when you let off it jerks to a stop. I know that a non engaging or slipping reverse means time for a new transmission...but how about this?

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1990 300d 2.5 turbo
1995 E300d

Brake problems can give the same feeling, just be sure.

I'm pretty sure it rolls freely in neutral, but I should double check. All 4 calipers are fairly new, but I am due for some brake hoses. Maybe could be the ebrake dragging only when going backward?

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1990 300d 2.5 turbo
1995 E300d