QuestionI bought a 1981 Mercedes 300D with automatic transmission which doesn't seem to shift correctly. When I looked under the hood closely I found a vacuum line was not connected. When I connected it the transmission was even worse --- rev's high before finally shifting into drive (3rd) gear. It doesn't seem to be slipping once it's in gear, but the 2-3 shift point is alot higher rpm than I would expect when I'm not flooring the pedal. I was told that this could be a faulty vacuum modulator. What is there to adjust on this AT and/or modulator? Where can I find info on it (it's not in the Haynes manual I bought)? Does the ATSG Trans manual cover these adjustments? (I did a complete rebuild of a GM700R4 tranny on my 89 S10 blazer last spring using the ATSG manual for it, so I like to think I'm not a complete idiot with AT's)
Thank You,
David Howard
AnswerHello David
Much more diagnosis is needed.
The good news is, a hard shift generally = a good transmission.
Bad news, it is generally vacuum problems, Bowden cable adjustment or bad vacuum modulator, there where five different modulators used on your model transmission as I recall.
The vacuum routing is "critical" for proper MB diesel transmission function.
Buy a MityVac or generic unit, a vacuum tester is the MB diesel owner's friend http://www.mityvac.com/
Go to the following link and correct all vacuum line routings under hood.
http://www.mercedesshop.com/shopforum/showthread.php3?t=105297
If they are all correct:
Check your Bowden cable adjustment.
http://www.mercedesshop.com/shopforum/showthread.php3?p=800066#post800066
http://www.mercedesshop.com/shopforum/showthread.php3?p=800055#post800055
More transmission adjustments data.
http://www.mercedesdismantlers.com/AutomaticTransmissionInformation.html
Further questions welcome, with more diagnostic data.
