300SD Shifting problem - PeachParts Mercedes-Benz Forum

Stevo · #1 05-05-2002, 12:41 AM

greetings All

My daughters boyfriend has just purchased a very nice 1980 300 SD and he has a shifting problem that someone might be able to help with. It is an automatic transmission. When shifting into second gear, the transmission disengages then hesitates before engaging again in the new gear.
Also, especially if the engine is still coming up to operating temperature, the transmission shifts HARD
throwing the driver's head back into the seat. We tried adjusting the transmission pressure control rod.
We are unsure how to determine when the pressure rod is properly adjusted.

Any help would be much appreciated as my cars are manual so I am not much help with this problem.

Stevo · #2 05-05-2002, 10:51 AM

Bill

Thanks for the reply. We'l search and see what comes up now that we know what to look for with the second problem and live with the first one.

He did score a very nice car. The guy in our local car lot didn't know anything about MBs and stuck it out "back" in the weeds cause it wouldn't start so when Matt offered a K he jumped on it. A new starter cured the problem and it runs great except for the tranny problem which an adjustment may help.

This MB fever does seem catching. My daughter came home from Xmax brake last year and fell in love with my manual 240D so I found a 78 240D manual for a graduation gift for her then her boyfriend catches the "bug" and finds this 300SD now my friend (boat trash) has just bought a manual 240D. I tell you, I dont know where this will all end.

can-do · #3 05-05-2002, 07:04 PM

Greetings Steve,

Does this '80 300SD have a solid tranny rod going down the passenger side of the block to the tranny? If it does we can probably fix your flaring problem with an adjustment. If you have the cable tranny downshift method than backing the white threaded nut that's on the valve cover out delays the shift, but in most likelyhood the modulator on the tranny itself will need adjustment for flaring if you have this shift setup. It's covered in numerous posts so I won't go over it here. The following site goes over adjustment of the modulator if you care to look and have this item on your car.

http://www.mercedesdismantlers.com/

Charles

can-do · #4 05-05-2002, 07:27 PM

Hi Bill,

My ole '80 had flaring between 2nd and 3rd gear and came to find out that the linkage was actually misadjusted. The rod running on the side of the passenger side of the engine block needs to be disconnected at the next snap coupling and pulled fully extended from the tranny and then screw in the cross-over connection so they just meet and connect together, pull pressure must be maxed out when adjusting. You must also get rid of any slop across the valve cover linkage as well. Doing all of this will cause your car to shift properly with acceleration as well as downshift under a load such as going up a steep hill without mashing the pedal down to the downshift button. This is all in the Haynes manual as far as the adjustment, and it does make a difference in performance as well as rid you of the flaring as this is simply a gap in linkage travel that causes this to happen on this setup. If yours is modulator and cable controlled, then the modulator is your most likely culprit and should be addressed to keep from wearing down your tranny clutches. Hard to believe that your mechanic would say that this is as good as it gets when it's not working properly, and the problem still exists.

Charles

Stevo · #5 05-05-2002, 08:06 PM

Thanks All

It does have the rod down to the tranny. With the link , info, and search we should be able to get a handle on the problem. Thanks all for the good scoop.