Mercedes Benz repair: transmisson, best guess, 300td

Question
I have a 1984 300td the transmisson will not go into gear in drive unless you rev up the motor to about 2000 to 3000 rpms. Reverse works just fine. After you get it going down the road it shifts  threw all the gears fine but when you stop again you have do it all again.I checked the fluid several times and is always ok. what could be causing this problem?

Answer
Best guess without hands on diagnosis:
Sounds like the transmission B2 piston may have fractured.
This is a possible DIY, but very messy.
Transmission fluid must be changed after piston is replaced.

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