722.6 Conductor Plt R&R - Solinoids? - PeachParts Mercedes-Benz Forum

l_turn9 · #1 05-27-2021, 07:36 PM

06 E350AWD - I plan to replace my Conductor Plate as regular maintenance and to hopefully fix my shifting problem. (It's due for a fluid R&R anyway) I'm not sure how to test the solenoids though. Is it necessary to test them? Can I hit them w/12v and listen for a click? Thanks -

bkc · #2 05-28-2021, 12:30 AM

You can test them (even when still installed on the conductor plate) for their resistance.

The three shift solenoids should be 2.5-6.5 ohms, ideally around 4, and ideally all three close to each other.

The two shift pressure solenoids should also be between 2.5-6.5, ideally around 5 and, again, ideally close to each other.

The PWM solenoid should be 2.0-4.0, ideally around 3.0

Just did this two days ago when I replaced my conductor plate (r170 SLK23) because of a cracking speed sensor.

Don't forget to change out the adapter plug, as well, and make sure everything is thoroughly clean (contacts, connectors, the two screens under the shift pressure solenoids - just pull out and lightly clean). Then put in 4.5 qts to get pretty close to correct level.

tjts1 · #3 05-28-2021, 09:35 AM

Quote:

Originally Posted by l_turn9

06 E350AWD - I plan to replace my Conductor Plate as regular maintenance and to hopefully fix my shifting problem. (It's due for a fluid R&R anyway) I'm not sure how to test the solenoids though. Is it necessary to test them? Can I hit them w/12v and listen for a click? Thanks -

What exactly are your shifting problems? The conductor plate either works or doesn't work. Are there any codes stored in the TCU?

l_turn9 · #4 05-28-2021, 05:00 PM

bkc - Thanks for the instructions! Much appreciated. BTW, what spec atf should I use?

;-)
Larry

l_turn9 · #5 05-28-2021, 05:31 PM

tjts1 - I believe I have 1 or possibly 2 problems (possibly related) = fails to upshift, and will not allow shifter to be moved back to P unless key is removed. Also cannot select C/S. These problems are intermittent but happen too often to allow car to be used.
That being said, I am also replacing my Shifter. I also have the upshift problem (at least I think it's a 2nd problem) which is the non-upshifting issue.
I am servicing the Trans in part because I believe the fluid should be changed at least occasionally. The car has ~160K on it and the Conductor plate, Filter and plug are cheap maintenance as I hope the conductor plate service will help problem #2. I am getting a P0705 code - Transmission Range Sensor Circuit Malfunction. I'm not sure where the Speed Sensor is - there are Speed Sensors (N2 & N3) shown on the Febi diagram of the 722.6 conductor plate. It appears the Speed Sensor solenoid connect to the Starter Interlock Switch as well as the Shift Sensors Solenoid & Pressure Solenoids. I'm still learning about the Speed Sensor system.. Any help you can provide would no doubt push me along and be very much appreciated!
Larry

bkc · #6 05-29-2021, 02:35 AM

ATF: MB spec 236.14. Although I have been told by multiple (reputable) tranny rebuilders that I can just use regular red ATF. What is important, whether I use the "official" spec or not, is to change the fluid (and filter) every 30-40,000 miles. This is what I am doing in my own two 722.6 vehicles, although I follow the spec on customer vehicles, just in case.

Typically, the front center speed sensor (one of the two on a little stick that wobbles front to back) cracks. I suppose, in theory, you could just replace that piece (if you can find it separately), but generally you might as well just replace the entire plate.

Regarding the other items: has any liquid gotten into the shifter unit (easy to spill into the opening, unfortunately) or has any ATF wicked its way up the harness into the TCM? Check for ATF in the adapter plug. Very common as the cause for weird behavior or codes.

Hope that helps!

Cheers,
-Bruce

l_turn9 · #7 05-29-2021, 03:39 PM

Hey Bruce - First, VIP your 93 300D 2.5T! I had a 91 I bought about 15 years ago and the rear suspension rusted out. If my legs were better I might have attempted to repair it myself. But I sold it to a fellow 124 enthusiast and it's back on the road. My favorite MB of all time and I miss it dearly!

re: Shifter - No, nothing was ever spilled on it while I have owned this car. Dry as a bone and I am confident it has always been like that. My wife is the primary driver and she doesn't drink in the car and no kids. So I don't think that's the problem.

re the Plate - I am replacing the Conductor plate so that will hopefully solve my problem. However, when I am changing things over I will test the Resistance of the Solenoids. We'll see what that tells me. The plate arrived yesterday and I think I found the little thing that flexes along the edge of the plate. Are you saying the Sensor itself cracks or the part of the Conductor Plate where the speed sensor sits?

re: ATF - thank's for the explanation - I may go with whatever red ATF I find for this change. BTW, your comment about changing the ATF is interesting. It's what I have always done but MB was seeming to tell us the ATF was installed for a lifetime and never needed to be changed. It's encouraging there are more doubters out there than just me ;-)

Thanks for taking the time to explain your experiences.... While I feel the W124 Diesel was the perfect MB, I still like the E350 - it looks and drives great when it works, but they went too far with electronics. With all the emphasis on EV's (Yuck) I wonder what t'shooting on them will be like? ;-) I wonder what a diesel W211 is like?

gmog220d · #8 05-31-2021, 09:36 AM

After researching which fluid to use in the '96 I went with Shell ATF 134.

See this post:
ATF "Alternatives" for 722.6?

From this thread:
ATF "Alternatives" for 722.6?

l_turn9 · #9 09-13-2021, 03:53 PM

Hi Gang -
I removed my 722.6 Valve Body today and will start removing the Conductor Plate shortly. After putting the VB on my work bench, I found the Solenoids do not have any dust covers on them. Should I order some? Did any Solenoids come without any dust covers?
TIA -

Zulfiqar · #10 09-13-2021, 05:01 PM

Looks like someone was in there before and tossed the caps, the caps are to assist in channelling all draining oil/ATF back into the pan and not get pooled in other spots - The 722.6 case is interestingly designed too - it has a spiral lip cast into it that allows smoother oil drain to the pan.

I would suggest you test the ATF for glycol or water damage and the contact pins for any signs of tarnishing. Your car may have the factory defected valeo branded radiator in it.

l_turn9 · #11 09-14-2021, 11:28 AM

you wrote: factory defected valeo branded radiator - that's interesting. I have never heard of that problem. Do you have any additional info? I'll do some research - thanks for the rad. info and the dust cover info.