Mercedes Benz repair: MerBenz 420SEL Transmission, ruptured diaphragm, vacuum modulator

Question
I own a 1986 420SEL. About 5 days ago was driving at 50MPH when the RPM
went to 4000 suddenly, car still ran but had downshifted to 1st gear. I slowed
down to 15MPH, pulled over. Was able to get car to shift up to second. Tranny
fluid was a bit slow, refilling helped but car did it again today. Vacuum pump
may also be going out. Is there a connection? What am I looking at in terms of
cost? Can you deduce the probable cause of the problem or do you need
more information? Thanks

Answer
Answer:
Note:
The only vacuum pump on your car is for the central locking system.

If the fluid was low, our first suspect is the vacuum modulator, a ruptured diaphragm allows fluid to be sucked from the transmission into the engine intake manifold, causing reduced engine/transmission performance, and low transmission fluid level.

Here are some links that should help you.

Transmission:
http://www.mercedesshop.com/shopforum/showthread.php?t=142395

Please e-mail me on the central locking issue you have.