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722.6 Slow shifting: fixed today by replacing trans conductor plate

13558 Views 26 Replies 6 Participants Last post by  Dave2302
The silver S430 has been getting a lot of TLC from yours truly. This stuff is fun. :)

The transmission's shifting felt kinda sluggish. It's never failed to shift, and it's not in limp-home mode, but the shifts would feel just slightly klunky--no banging noises, just a feel--and it was starting to get very gradually more mushy, if you will. There were no codes. It'd probably be fine for another 10,000 miles, but I just don't like sloppiness on a Benz. Better to deal with it sooner, when I can take my time and do it right.

Some Googling and STFF'ing said something about the speed sensor typically causing this, and the way to deal with one of those on the 722.6 transmission is replacing the conductor plate with a new one. Since I already had a plate handy, I thought, might as well try an experiment.

Sure enough, it worked. Shifts did firm up considerably, which I consider a good thing. The "klunky" feeling is pretty much gone. I had done the transmission fluid and filter exchange (the full 14 liter version) about 5,000 miles ago, and apparently dropping the tranny pan really does result in a loss of nearly exactly 4L of fluid. Four more liters of the good stuff took care of things. Also replaced that made-in-Taiwan Meyle filter with a genuine M-B filter, as well as a new trans electric connector (also M-B brand). Hey, those have to come out anyway, so might as well, right?

The job took me about 5 hours, since it was my first one, and as usual, I'm doing it on the street, i. e. no lift. Actually, since my buddy's borrowing my jack, I did it with the car's front end up on a pair of Rhino Ramps. :) Yes, it can be done. It's a little awkward getting the valve body back in, especially if you have long arms, but it's certainly doable. Next time, it'll probably take me about 2 hours since I now have a better idea of how to do it.

While I was at it, I checked the resistance of the solenoids. All of 'em are right within spec; matter of fact, they're at dead-center of the acceptable range.

Miles on the car are 143K. Tonight's test drive was a pleasure. Well, driving that car always has been, and now it's even more so.
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Hi all, I came here to start a new thread about my 2005 S600's 722.6 transmission, but found this recent one so I thought I'd try tacking on.
Bought this car a couple months ago sight-unseen from a dealer on Ebay, nothing mentioned in the ad about the trans. Got the car (it was delivered), go for a spin, and I think, "Man, this transmission's slipping." For sure in 1st gear, maybe others, and the shifts aren't at all what you'd call crisp.
Read up on the forums, did the adaptive reset thing, and that helped the 2-3, 3-4, etc, shifts, but it still seems to be slipping starting from a stop. As in the RPMs go up to about 1500 just to get the car moving, even closer to 2000. At idle on a level road it'll hardly pull itself.
Then I remembered that my 2000 Jaguar XJR had "a Mercedes Benz transmission", did a little research, and lo and behold it was the 722.6. I absolutely LOVED that transmission, best automatic I've ever had (out of maybe 20 cars I've bought over my life). Okay, same transmission, so there's definitely something not right with it. I'd read about the 13-pin connector causing problems, so I bought one of those, some fluid, and a new filter, figuring I'd just swap the connector out and see if that helped.
But then I hooked up my STAR system to see if I could learn anything about what was going on, and wow, a TON of codes. I had read up on the conductor plate, read some how-to's, and watched some videos, so I feel comfortable I could replace that if necessary. I'll list some of the codes below, but what I'm trying to figure out is if people think just the connector would fix all these, or if it's more likely the conductor plate. I don't want to have to drop the pan twice.
There's a full 3 pages of codes in the error log:
P2100 - The internal electrical check of component Y3/6y3 (1-2 and 4-5 shift solenoid valve) has failed.
P2101 - " " " " " " " " " " " has a short circuit to ground.
P2102 & 2103 - same messages for the 2-3 shift solenoid.
P2104 & 2105 for the 3-4 solenoid.
P2106 - internal electrical check of torque converter lockup PWM solenoid valve has failed.
P2107 & 2108 - same for the modulating pressure control solenoid and shift pressure control solenoid.

And some others. Those electrical-type codes made me think that it might just be the 13-pin connector, but then we get to:
P2502 - The gear is implausible or the transmission is slipping. Then there's P2560 through 2564, those same words, but for each gear.
P2507 & 08 - Engine overspeed Y3/6n2 & 3 (speed sensor 2 / 3)
P2602 - The voltage supply of the valves is faulty. & 2603 for the speed sensors.
And from what I've read of speed sensor errors, that points to the conductor plate.

So what do you guys think, buy a conductor plate and just do it all at once?
What else should I do while I'm in there?
Should I do the shift linkage seal mentioned above, even if it doesn't appear to be leaking when I get under there?
Should I buy any of the parts that Sonnax makes to deal with worn bores in the valve body? The car has 117k on it.
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Well that's certainly not what I wanted to hear! I appreciate your advice, but for a couple hundred bucks for a conductor plate I might just have to try it. If nothing else I'd have a new plate to stick in a known-good used trans. After all I've read about the 13-pin connector and the conductor plate fixing people's problems, I thought surely the diagnosis would be to try that. I'll post back in a couple weeks when I'm done and give you the opportunity to say, "Told ya so!" ��

Cowboy: good idea. Once I get the plate out I'll test the solenoids. Resistance checks I can do easily enough, but I don't know yet how to do "the actuation tests." I'm sure it's here on the forums. Maybe the $300 one is good and I only need to replace a couple $75 ones.
I don't know if the codes were stored or current, because my laptop's battery was dying so I quickly saved the error log (that's what I posted from last night), and looking at it again, it doesn't designate which. It was my first time using STAR, and I was actually troubleshooting something else when I came across the transmission menu and took a peek at that. I'll do what Dave said and clear the codes this weekend and see what comes back.

Thanks for your help, guys!
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Try this before a new transmission.
Thanks for that. Before I saw your post I ordered a Mercedes branded one from Amazon for 127.94 with free shipping. Will put that in next weekend and report back.

Also ordered (from Rock Auto) the Sonnax Master Overlap Control Valve Sleeve Kit - 68942-05K
based on some things I read. I don't think it will help my specific problem, but with 117k on the transmission they may help shift quality, and I'm going to have the valve body out anyway. 36.79 plus 6.99 2 to 3 day Fedex. Every place else wants about $67 for that kit.
What's the "sheepish look" emoticon?

So all those fault codes I posted? That was the "Full list of fault codes and events" from DAS, more than halfway down the ETC screen. Boy do I feel dumb. "Fault Codes" is the second from the top. I guess I was so fixated on it being an electrical problem that all those electrical-type codes made sense to me.

That is "chuck parts at it until it's fixed", and IMHO that seldom ends well, and always costs far more than proper diagnosis.
Proper diagnosis is, first clear all codes, then see what comes back.
What about the 'slipping', that indicates Worn Clutches or Torque Converter breaking up internally.
If you pull the plug from the Trans, it should still Drive and Reverse without slipping.
So Dave (or anyone): I went to clear the fault codes yesterday, but there were none. I thought maybe I'd cleared them the other day, but maybe there never were any. So I drove it to work today, about 12 miles each way, and NO FAULT CODES are set. I know that's not a very long time/distance, but three Events did come back, but I'm guessing they're not related to the driveability issues:
P2314 - "One or more messages from control unit N93 (Central gateway control unit) are not available on the CAN bus. (CAN timeout fault.)"
P2315 - same words, but for A1, Instrument cluster.
P2316 - same words, but for N19, Air conditioning control module.

So let me get back to basics, here's what the trans is doing:
Barely pulls itself in Drive when idling. *barely*. I had this same trans in a Jaguar XJR and that thing would idle up a pretty good grade.
Ease into the throttle and it's 1500 to 2000 RPM before it really starts to move. This thing is "slipping", no doubt in my mind, and it's embarrassing driving around parking lots because I'm having to rev the engine pretty high just to get it to go. I think it does this in both Sport mode and Comfort mode, which if I'm not mistaken, just starts you out in 2nd. At least when I got the car it was in Comfort mode and I attributed the "feel" of slipping to that, but went to Sport mode and same thing.
After getting into 3rd and higher it seems to act normally, no hesitation between shifts, no crunching/grinding/rumbling, no apparent "slipping", and the tach seems to agree with road speed.
I've tried to feel for converter lockup, but can't say I've felt it, even though part of my trips today were on highways at 65+.
At the Transmission Control Unit (or ETC as DAS calls it) there's NO indication of trans fluid wicking up the wires.

Now let me add something I forgot initially:
Sometimes when putting into Drive or Reverse, the trans doesn't engage. It happened this morning after I dropped my daughter at summer camp: parked, car off, 5 minutes later start it, select D, and nothing, it was as if the car were in neutral. Slipped the selector to N, back to D, and it engaged.
The same thing has happened in Reverse, once when the car was pointing downhill and I was trying to back up, but it literally rolled forward, no kind of engagement or drag. Put in P, back to R, and all was good.

Early on I bought this dipstick:
and I don't remember exactly, but I think the fluid level was a bit more than half. After a drive, so trans was at operating temp, level ground, in Park. In hindsight, maybe I'm misreading that, because I think the upper mark is for 80C, while the lower mark is for "cold", is that about right? I was reading it like an oil dipstick: "between the marks is okay."

So tomorrow I'll check that again and top it up if needed (with Pentosin).
Assuming that doesn't help, what next?
Do these symptoms (especially the no-go when in gear) point to the torque converter?
I'd still like to drop the pan and see if there's anything in there; that would be a sure sign. I have the $12 electrical plug, so I'll replace that while I'm under there.

If it's not the TC, how likely is it I'd be successful "rebuilding" the trans? I've rebuilt 3 engines, done some heads, cams, timing belts, differentials, etc. I've got all the normal kinds of tools, including torque wrenches and gear pullers.
Or should I just get a rebuilt or junkyard one, which would be quicker.

Thanks again,
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First up, Trans and Converter must be done together, do not change one without the other, it usually results in more grief than it's worth, and you will end up doing it again using both parts
To rebuild a 722.6 and Converter properly costs me £900 in parts.
There is a load of special tools needed to do this properly
To Rebuild and Fit I retail at @£1600 + depending on exact vehicle.
If I were a DIY and good with spanners I'd buy one with a Guarantee from a Breakers, pref low mileage, in UK around £450.00.
You MUST flush out the Oil Cooler and Lines.
Dave, thanks again for all the sage advice, and for putting the costs in perspective. (I'm in the US, but can do the conversion.)
So I just drove the car around to heat up the trans, checked the level on a flat surface (running in Park) and found it about 3/4 of the way between the highest 25C mark and the lowest 80C mark (finally noticed the numbers on the dipstick). So if the bottom of the dipstick is to the left, it looked something like this:
I topped it up until it was almost exactly at the upper "80C" line without going over.
Can't say it acts any differently.
Based on what Tusabes said ("Mercedes don't creep like other cars"), I'm now wondering if this is just the way this beast is. If I hadn't had the 722.6 in my Jaguar XJR I wouldn't have known the difference, but still, it doesn't feel "right" to me.
So does anybody know why the two applications would act differently, if in fact they do? Would that be on account of the torque converter, maybe?
I have some coworkers who are long-time Mercedes owners, so I'll get one of them to drive it and see what they think.

I'll finally crawl under the car this weekend and if it looks like the connector is leaking I'll replace it, and probably go ahead and drop the pan to check for debris. Will advise what I find.
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Good read, thanks for that. Some of the posts were talking about (C)omfort mode starting you off in 2nd gear, which I totally get. My wife's Volvo XC90 in Wet mode (2nd gear starts) feels about like this car, but probably not quite as slippy. And my XJR, even in Comfort mode, didn't feel like this car does in Sport mode.

But what gets me is, aside from just being in Sport mode and "assuming" you're in first gear, when I've manually SELECTED 1st gear, and the display shows "1S", it 1) hardly pulls itself, and 2) will get to almost 2000 RPM before it really feels like the gear is engaged and it's "pulling".

Another data point to consider: I've NEVER been able to spin the tires with this car (yes, ESP off). Not that I've tried a lot, but my boss had an '04 S-Class with the same twin-turbo V12 and he talks about chirping the tires in the parking garage just trying to take off, or chirping on the 1-2 and 2-3 shifts, or "breaking loose" at highway speeds. So today after I topped up the trans fluid, I went to an unused road in my subdivision and tried a couple times to brake-torque and spin the tires, level dry asphalt, ESP off. Just a bit of a squeal, like a squeegee makes on glass, but certainly wasn't spinning the tires. Don't get me wrong, it took off like a bat out of hell, way faster than the 370HP Jaguar did, but nothing like the Youtube videos I've seen where guys are smoking the tires at will.
The Check Engine light is not on, and there were no motor codes yesterday when I checked, so what am I missing? Do I need to go to Dyno mode? (Btw, I'm 53 years old and don't go around spinning tires, but if I *should* be able to in this car but can't, does that say anything about the trans? And what about peak RPM with the brakes applied? I didn't note what it was, but would that indicate anything about the converter? Other than "you're going to need a new one if you keep doing that!")
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