Mercedes Benz repair: 1985 Mercedes Benz Diesel 300 SD- Transmission, mercedes benz diesel, bowden cable

Question
The Mercedes won't shift into drive. Reverse works fine. The car will act as if it is in neutral and eventually shift after the engine is reveing at that point it will work normally. Is this an adjustment or is the car in need of transmission work?

Answer
Here are some possible issues:
* Low fluid
* Vacuum Control Valve
* Failed vacuum modulator.
* B2 servo/piston
* Bowden Cable broken
* transmission slipping

Transmission modulator adjustment
http://www.mercedesshop.com/shopforum/showthread.php3?p=791654#post791654  

transmission slipping need expert advice please
http://www.mercedesshop.com/shopforum/showthread.php3?p=566361#post566361

Vacuum Control Valve
http://www.mercedesshop.com/shopforum/showthread.php3?p=869411#post869411

Bad Vac Control Valve?
http://www.mercedesshop.com/shopforum/showthread.php3?p=834716#post834716

B2 Piston Failure
http://www.mercedesshop.com/shopforum/showthread.php3?p=1048115#post1048115

722.118 transmission B2 servo/piston         *B2 Piston*
http://www.mercedesshop.com/shopforum/showthread.php3?t=131124

I Am Really Hurt Now        *B2 Piston*
http://www.mercedesshop.com/shopforum/showthread.php3?t=106317

C220 won't go forward. HELP!         *B2 Piston*
http://www.mercedesshop.com/shopforum/showthread.php3?p=732079#post732079

B2 Piston W124
http://www.mercedesshop.com/shopforum/showthread.php3?t=109035

Two threads the same title, but different authors and content.
Bowden Cable
http://www.mercedesshop.com/shopforum/showthread.php3?t=54776

http://www.mercedesshop.com/shopforum/showthread.php3?t=41603