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#1
03-27-2013, 09:01 PM
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transmission modulator
I have a '91 420SEL with a green transmission modulator valve.
I have not removed it but I have cleaned it very well and can find no part number. I ordered one through EPC for my VIN and it is black (126 270 91 79). On the Mercedes-Source web site they mention that this black unit is an improved part over the older original unit. What I am concerned about is that they are usually color coded for a very good reason and of course I am no longer green if I use this one and frankly don't know enough to know what is correct. I know how to remove it but can not find the reference for setting up the new unit whether I acquire another green one or use this new black one. According to the data card I have a 722.355 automatic but I do not find a number on my tranny to verify this. I am the 3rd owner so there is no solid way to know if this is the original tranny or not. jimm1009 here or jimm1009@yahoo.com E-mail would probably be better as I am relatively new to this forum. 
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#2
03-28-2013, 07:42 AM
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Write me, please, the VIN of your 420 SEL.
I'll going to help you... 
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#3
03-28-2013, 08:16 AM
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I think they are just color coded to aid at the factory, the modulator may have been tailored to a specific engine/chassis combination. As far as changing the color to black and saying it is an improved unit, many times manufacturers make changes after the car is built and will do things like this after the production run, MB is especially known for improving things long after a car is out of production. The changing colors helps ID what you have. If yours is green and the new one is black I'd assume you are getting the updated part. Very possibly this is your only new part option, you coud try to find a green one used somewhere, but is shooting yourself in the foot in my opinion.
I can't tell you if the black one is still tailor made for your engine and chassis combination, but would be willing to say it is. You could try looking up the modulator for other engine/chassis combos that ran a 722.3 of similar vintage and see if it is the same pn. Once in awhile I would need to adjust the modulator after instaling a new one, I think they must have a quick test they run for adjusting it and usually felt fine, if you shift quality sucks (too hard or soft)you can adjust it if you need to very easily.
__________________
Click here to see a photo album of my '62 Sprite Project Moneypit (Now Sold)
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#5
03-29-2013, 01:14 AM
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Correct vacuum modulator valve: "black", p/n 126 270 43 79 and 126 270 91 79 (optional).
Modulating pressure = 3,8 bar. Ciao!
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#7
03-29-2013, 10:43 AM
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#8
04-07-2013, 12:17 PM
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After putting a slow, easy 90 miles on my car this week I took the air cleaner off again to check for small seeps, etc.
I had made a comment earlier about my bowden cable not having any tension on it while the tranny was empty and I not receive any responses any so I thought that if I filled the tranny up with fluid and got it moving that it may be o.k. It is still loose as far as tension on the bell crank at the left rear side of the engine. I can move this lever by hand whether the engine is running at idle or turned off. On the 1987 420SEL in the parts yard there is tension on the cable in that the bell crank takes a moderate finger pressure to move it back and forth. I now believe that my bowden cable is bad. The version that I have is in the attached drawing from EPC and the one to the far right of the three units. What is odd is that all three units are identified as 204 and there is only one 204 p/n which is 126 300 29 30. I am charging the camera battery in order to take a picture and will post it here in just a few minutes. If I need to change this cable I expect some trouble in the form of harassment. Does anyone have a picture of the lower end of a new or good serviceable cable? I believe that mine is broken at the bottom end and that lower two or three inches is in the transmission upper housing. I assume that this end can come out with gentle pressure from some need nose pliers? I hope that there is no setup procedure for the cable change in the form of rigging. Will update with the picture ASAP. Edit: It seems that I can not attach a jpg format picture for some reason. The bell crank for the cable is just forward of the throttle cable on the same pivot. I can move this freely about 1 inch of travel and there is zero tension on it. URO aftermarket is $25 and the OEM from parts.com is $195. Is is worth trying to acquire the used cable from the 1987 420SEL for $10 or so? Edit @ 15:15 Sunday; I went to the salvage yard a little while ago and disconnected the bowden cable from the tranny on that car and the lever (#225 in PDF) was connected to the lower end. Since someone purchased the transmission oil pan I could reach up in there and actuate the lever with my finger and in feeling the upper end it appears that there is a 90 degree bend to form a hook that is almost 1/4 inch long. I don't think that my lever has a hook that long on it so it may have broken off but am not sure at this point. The only way for me to know is to drain the fluid again and remove the pan, disconnect the bowden cable, and feel the top of the lever and see if it is the same. If it is o.k. and my lower end of the cable is not internally damaged or broken, perhaps I can reconnect it and make it work. While I am certainly not an expert by ANY means, it appears that this could be my transmission issue of kicking down and then releasing about 5 times in 5 to 10 second cycles while accelerating up to about 65 MPH while merging onto the interstate highway. Last edited by jimm1009; 04-07-2013 at 04:24 PM.
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