Erratic Shifting
 

Hi Folks,

My 82 240D with 150k miles has me a little stumped. Being that the trans shift timing and quality is strictly controlled by vacuum I figured that the trans is either shifting well or not depending on if there are leaks in the system. When I originally got the car the vacuum system was all messed up. Since then I have:

Replaced both 3/2 valves and all the soft lines and connectors

Changed the trans fluid with new and new filter

Since those repairs were completed the trans had been shifting great, until a few days ago when it would randomly hold on to gears, or randomly downshift to 3rd from 4th going 25/30ish mph with light throttle input.

I'm a little stumped because it shifts perfectly 95% of the time but then suddenly decides to hold hears longer and shift very hard. Then it will stop out of the blue.

Does not appear to be temperature related since it does it hot or cold.

I have unplugged the kick down switch to make sure that is not the culprit.

A better description of the symptoms would be helpful.

Check the tranny oil level really carefully and properly. Usually there are more consistant issues though when it is down a little.


Could be something periodically sticking in the valve body as well. Or the governor. A container of transmission cleaner and reconditioner might help.

just to follow up on this for anyone in the future... BOTH new switchover valves I bought from eBay (brand MTC) were defective.

Once leaks vacuum testing with the hand pump, while the other does not leak enough vacuum when depressing the piston and blowing through.

Very frustrating, thinking I might just buy the new OEM MB units.

This is the switchover valve where one nipple is always open to the atmosphere? Hooked up to the ALDA? Thinking about my 1981 300SD which has a new switchover valve.

If he is talking about affecting the transmission, I think he is referring to the valves on top of the valve cover.

Yes, in my particular car the valves on top of the valve cover are used for controlling shift quality and I believe timing as well.