1992 300D 2.5, which transmission modulator, black, blue or red? - PeachParts Mercedes-Benz Forum

Wayfarer · #1 06-29-2010, 10:14 PM

In the process of trying to diagnose my transmission problem, I began to think that the modulator installation might not have been done properly. In researching it, it appears there are no less than three separate vacuum modulators for the transmission in my car, black, blue, and red! The one I had installed after which the problem started was black (A126 270 91 79). I subsequently called Performance Products (I had an old catalog lying around) to make sure that was the correct part. They said oh no, that was the incorrect part, I needed a *red* modulator (part no. A126 270 90 79), which I then ordered.

This week it came in the mail and I was about to install it but I thought to check the MB EPC site just to make sure this red modulator was the correct part. Well the EPC site has two possible modulators, one black and one blue, listed for my car depending on the serial number of the transmission. I crawled under my car, got the serial number, cross referenced it with what was on the EPC site, and it said I needed the *blue* modulator (part no. A126 270 94 79)!

So here I am, needing to make sure I have the right modulator, and the three parts suppliers I've checked with each say I need a different type of modulator.

Can someone tell me definitively which modulator is correct for my car?

Black (A126 270 91 79) / aka A126 270 43 79
Blue (A126 270 94 79) / aka A126 270 40 79
Red (A126 270 90 79) / aka A126 270 57 79

The full number string off the side of my transmission is:
124 270 81 00 722 418 0 3207006

compress ignite · #2 06-30-2010, 03:06 AM

If you've "crossed" your tranny serial number with the EPC range...
(URRKK and Verified with a Live KNOWLEDGEABLE MB parts specialist)

Whatever the EPC calls for is the correct part!

BUT, I'll tell you what, ALL THREE of The Major MB OEM parts suppliers
ONLINE are showing the BLACK/Schwartz/Noir Modulator.

You've, P.M. Traffic

Wayfarer · #3 06-30-2010, 08:39 AM

Quote:

Originally Posted by compress ignite

BUT, I'll tell you what, ALL THREE of The Major MB OEM parts suppliers
ONLINE are showing the BLACK/Schwartz/Noir Modulator.

The black one is what I have in there now. I'm just trying to make absolutely sure I have the correct part. The Perf Prod gal was absolutely sure it was the red one, I even called their customer service just to verify and they said the red one was correct. Next stop, the two parts guys you pm'd me. Then I'll report back. Thanks.

Wayfarer · #4 06-30-2010, 10:23 AM

I called those two MB parts specialists you pm'd me and they both said that the *blue* modulator is the one I need.

MB changed from black to blue on the 722.418 transmissions as of serial number 3015840. My transmission serial number is 3207006, which is, of course, *after* the change to the blue modulator.

Please, please let this be the reason for the suddenly appearing downshift clunk when I put in the new black modulator. It looks like that was the wrong part!

I guess all the parts houses that say it's black are wrong. Perf Prod are just way out in left field with the red

.

Thanks for the help.

Just got off the phone with my local MB dealer, they concurred that blue ("blau") is the one I need, so I went ahead and placed the order with them. Part should be in mid next week.

Now that I think of it, the old-style modulator that was replaced when this problem all started was blue. At the time, I was told that the new black style superceded all others. Guess not.