722.6 Slow shifting: fixed today by replacing trans conductor plate

13631 Views 26 Replies 6 Participants Last post by Dave2302, Jun 29, 2017

cowboyt

Discussion Starter · Jun 18, 2017 (Edited)

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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cowboyt

Discussion Starter · #3 · Jun 20, 2017 (Edited)

No, I didn't do the shift lock linkage; didn't know that needed to be done. I did notice there are screen filters under some of the solenoids; were you referring to those? If so, I did take those out and look at 'em, and they looked clean. Never occurred to me to replace the springs. I've never taken a valve body apart on *any* transmission, so this would be a new adventure.

I'll remember these tips for the next one, though. I'm guessing the S600 will need it next, possibly also the E320 CDI project car.

Much care was taken to make sure the transmission didn't get any dirt on it. Soon as I got that valve body out of there, it went straight inside, on a clean, lint-free environment, for the work.

Might be worth it to get a spare 722.6 transmission just to learn how to take certain things apart on it and put 'em back together, without risking messing up a daily driver. That will be a little while until I can get a garage, though.

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cowboyt

Discussion Starter · #5 · Jun 21, 2017

Currently on a road trip. My car's driving great. Even after a 16-hour drive, I didn't get tired; W220's are wonderful for cruising long distances. I really do see why people buy these cars.

However, I did notice that the computer's fuel mileage is now...um...a bit off. It's showing between 28 and 29 mpg fairly consistently. However, my handheld calculator tells a different story. After 564 miles, I filled up with just under 23 gallons, which I found interesting given that I wasn't on empty yet. Stated fuel capacity of a 2003 S430 is 23.2 gallons. The fuel gauge was just a little ways into the orange "R" region, so I might've been getting a bit of--shall we say--"country" fuel dispensing readings. Alternately, this pump might have a different cutoff calibration (gasoline vapor pressure) than others I've seen.

Either way, it's a far cry from the 28-to-29 mpg that I was seeing. I recall the car computer's numbers being much closer to hand-calculated values in the past.

There's a Costco on the way home. I'll try filling up there and seeing what we get. Will update this in the other thread about W220 fuel usage accuracy. Am keeping all fuel receipts for this purpose.

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cowboyt

Discussion Starter · #9 · Jun 23, 2017

It would be interesting to do the resistance and actuation tests on those solenoids. If enough of them are bad, then Dave's probably right in his suggestion of a good used or rebuilt transmission. One of those solenoids is US $300. The others are typically around $65 to $85. All of mine checked out OK, so the conductor plate replacement made sense in my case.

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cowboyt

Discussion Starter · #10 · Jun 23, 2017

@Theinkdon: Those codes you saw...since you have STAR, were the transmission codes "stored" or "current"?

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cowboyt

Discussion Starter · #16 · Jun 25, 2017

Just got back from the road trip. 1,600 miles later, I can now report for sure that the new conductor plate *did* fix my issues. The transmission shifted very well the entire time, and it feels good 'n' solid. Matter of fact, the entire car feels solid. I guess that's what happens when one actually fixes issues on his car.

After 12.5 hours on the road, including a stop for a late lunch, I don't even feel tired...just a little hungry. A bowl of Shredded Wheat should fix that nicely. Got through telling the neighbor's son about how the car behaved on this trip (he's home from college), and that's how he describes his Dad's 2012 C300--silky smooth. Benzes apparently just cruise...and cruise...and cruise.

So, apparently I should buy a lottery ticket. :-D

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cowboyt

Discussion Starter · #18 · Jun 25, 2017

Normally I would agree with you, but I had also done the oil and filter exchange (the 14L version) about 5,000 miles ago, so it's pretty much all new fluid in there. But you are right in that there were no transmission codes showing up. Fundamentally, my trans was in pretty good shape when I got the car, and that may not be the case with Theinkdon's situation. I hope it is, of course, but Mr. Murphy has an interesting way of making his presence known....

Discovered another little issue, though; the AIRmatic pump is definitely struggling. I could hear it on the trip; it sounds like it's knocking (bop-bop-bop-bop, in rapid succession). It takes *forever* to get the car to rise up those 2 cm or so when I hit the Raise button. This is probably because when I got the car, the right front AIRmatic strut was definitely leaking. This was one of those "Stevie Wonder could see the exoxy seal had failed" kind of situations. I figured then the pump was starting to go from overuse. That's also partly why I got the car for what I got it for. So, looks like I'm replacing an AIRmatic pump, and fortunately, I happen to have a new one handy. That part will go in another thread.

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