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722.6 Slow shifting: fixed today by replacing trans conductor plate

13566 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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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.

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 :wink

To rebuild a 722.6 and Converter properly costs me £900 in parts.
3 hrs R&I, 1hr Road Test, back on Lift, Leak Check, Oil Level Final Check
8 hrs Strip Clean Inspect Rebuild.

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. If your breaker is honest about "good" and "mileage" you can fit and forget :wink

You MUST flush out the Oil Cooler and Lines.............

A couple of "Kooler Clean" Aerosols are a good DIY, we have a special Air Powered pulsating Paraffin Flushing plant :wink


Cheers Dave
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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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:laugh , I'm 55 years old and DO light 'em up at times :wink

I have W220 and W203 with 722.6 and both cars do creep slowly on flat ground.

The Supercharged Jaguars with 722.6 drive pretty much the same (Trans Wise) as the Mercedes, just slightly different Shift Points Programmed into TCU :wink

They also suffer from all the usual 722.6 problems, which is no surprise really as the Trannys are Identical :wink
Interesting at that time that Jaguar felt ZF couldn't build a trans to cope with the S/C Jag's Torque :laugh

Mind, they still can't, Audi and BMW (ZF Trans), they are regular visitors with Trannys gone "Bang" :rolleyes:
And when they go, boy are they "lunched", busted sun shells, drums, gear sets etc etc :big laugh:

Cheers Dave
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Perhaps Dave can step back in and tell us if there is an RPM test for the torque converter on the W220. On the Porsche 928 (and other cars), there is a test where you stand on the brakes and floor the throttle, and see what RPM is developed. (Yes, I know that the computer usually doesn't like for you to do that on the W220.)

Years ago, I was tuning an Olds Cutlass and discovered that I could floor the throttle, and without lifting my foot, could make a right-angle turn and smoothly drive out of the parking lot. The V-8 engine was running perfectly - turned out that the torque converter sprag clutch had failed.

Wally is correct, you can't really get an accurate stall figure for the MB due to the Electronics stepping in.

It's irrelevant here anyway.

If the Converter is breaking up, then the Trans will have some form of contamination / wear, and Vice Versa.

This is why a decent Trans Specialist will never change one without the other, unless of course the Converter has a cracked weld on a foot or some such, but even then they will be Extremely Specific on what exactly is covered by any Warranty they offer :wink

It just isn't good practice, and usually comes back to bite your @ss :wink

If I could drive this car I could tell him exactly what is wrong but this is years of Transmission Experience, and a "feel" thing.
No amount of Videos, Fault Descriptions etc etc can make up for "Seat of the Pants and Under the Right Foot" senses :wink

But, from the "it almost gets to 2000 rpm to pull away in 1st or 2nd Gear", (assuming of course that it is actually in 1st / 2nd Gear, and not stuck in 3rd or 4th), it is a 99% certainty that the Trans and Converter needs replacing. And if it is stuck in 3rd upwards, with "No Codes and display indicating 1st / 2nd", then it is likely a complex internal fault beyond DIY Capabilities / Equipment and Cost Effectiveness (LOL is Effectiveness even a proper word) :grin.

The most economic solution for a DIY guy is Good Used :wink

Cheers Dave
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