Mercedes-Benz Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
169 Posts
Discussion Starter #1
Last night I finally got around to changing out the transmission modulator on my 81 240D. There is a VERY noticeable difference, but alas, it is not quite right..
For starters, I'll give some background. The problem with the car was that it would shift from 1st to 4th by 25mph which made for extremely poor performance. I have not driven the car very much over 40mph due to the fact that at this time, I only need it for under 10 miles a day of in town driving. When I would get around 40mph, the engine would start to feel like it was working too hard to be only going 40. Past 40mph was just downright nerve racking so I didn't do it very much. So, a vacuum test singled out the fact that it was the modulator. The line was holding NO vacuum. I have the red modulator on my car so I ordered one.

Last night I put the car on ramps and went to work. It was hard to get the old modulator out, but I was able to do so with channel locks. The novice that I am was not sure if there would be tranny fluid coming out, but I was ready for it when it did. While comparing the old modulator to the new one, there was a spring with a little rod that was attached to the old one and not included with the new one. Am I supposed to replace that rod, or is it a part of the modulator? See pictures - the old one is mine, the new one is the stock photo from autohausaz.
So after installing the modulator, I refilled the transmission fluid to the correct level and went for a test drive. There was a very noticeable difference. This was last night and admittedly, I did not check to see where the oil pressure was as I was more concerned with the change in shifting. First to second is great (15-20mph) and second to third was a little quicker (maybe 30mph). It would not shift into 4th gear although it handled much much better at 50mph to 60mph. The engine was quieter than it was before at 40mph..

It was getting late so I only made a few adjustments and ended up back where I started. This morning, I was driving my son to school and I noticed that it was slipping (slightly) between first and second and my oil pressure is now low. Instead of the guage being all the way to the top most of the time, it barely rises above the mid point.

What did I do? Am I at risk for major damage? How is oil pressure and the transmission modulator related? Any help will be appreciated. Thanks.
 

Attachments

·
Registered
Joined
·
1,279 Posts
Transmission oil system and engine oil system are totally different. Did you knock the oil pressure line loose under the oil filter canister or pinch the line? The oil pressure guage is mechanical, not electrical.

Did you check the engine oil level?
 

·
Registered
Joined
·
169 Posts
Discussion Starter #3
well as it turns out, you have to have oil in the car in order to have oil pressure. i just checked it on my lunch break and somehow it was extremely low. Friday when I was filling up, I checked and it was at the top notch on the dipstick. There is oil on the block, but I have seen no puddles under the car anywhere. I recently changed the valve cover gasket and tightened some leaking hose clamps. I thought that eliminated much of the problem. I guess that is another question for another post..
So should I have installed a new spring on the modulator? I realized while driving the car at lunch that there is a delay from the point when I press the accelerator and when the car starts to move. It actually jerks a bit when I start to move. It does NOT slip from 1st to 2nd when I let the engine slow to an idle before accelerating. sometimes when I come to a stop and the engine is slowing down, it (the engine) comes to an idle with a jerk. Obviously the modulator adjustment is wrong.
Any other ideas?
 

·
Registered
Joined
·
1,279 Posts
Have you checked the vacuum supply to the modulator?

When was the last time the fluid and filter were changed?

Also, have you checked the linkage or Bowden Cable? I believe the 240 uses linkages instead of the bowden cable.
 
1 - 5 of 5 Posts
Top