Dingleberry

this doesnt always happen but sometimes when i let off the throttle at speeds between 25-35mph, I can see the RPM's drop down to 900 or so, which I believe is the converter unlocking. When I get back on the throttle, the RPM's will climb to 2000rpm where the RPM's abruptly drop down to 1700rpm (converter locking up, i'm guessing) That abrupt drop is so sloppy, it jerks the car. Any ideas? No, I don't have glycol in my ATF...

cliffs:
-traveling between 25-35mph
-let off throttle
-get back on throttle
-jerk

ohlord

by doing a reset of the trans to factory default.
Easy cheap way of returning your shift points to factory settings.

Dingleberry

you mean the throttle adaptation reset trick? the one where you hold the throttle down with the engine off, key in on position. i've tried that

LILBENZ230

I think the 722.6 transmission converter locks up almost immediately upon pulling away from a stop and doesn't unlock till you stop again. This is what Glyn M Ruck has described to me is the appropriate behavior for this transmission. My car doesn't behave the way you describe, and never has, but I'm a C230. Maybe it is different for AMG models.

Edit: I should have elaborated. My car never "coasts" the way you describe. At any speed, if I lift off the throttle, the RPMs decrease gradually with speed, the car will not "coast", so to speak. So Glyn is correct in my case.

Edit 2: Key should be in ACC position when doing that reset, not in ON position.

Dingleberry

yes, i've read that post from glyn. i'm hoping he can chime in, since he's pretty knowledgeable.

i should mention that sometimes my car coasts with the RPMs gradually decreasing with speed. (it always does at speeds other than 20-40mph) when this is the case, no surprise i get no jerk because the converter isnt locking back up. but for some stupid stupid reason, I THINK the tcu occasionally decides to unlock the converter on decel (this is only an issue between 20-40mph aprox) i can take a video if this helps

you're wrong about the reset btw, see original thread here

Glyn M Ruck

I hate to say it but it sounds like a valve body or TCU problem. The converter should not unlock as you describe. Have you checked the TCU plug for oil leaks? It's too fast for the 1st gear one way clutch failure. Does it do it in both C & S modes?

Check for leaks
Try and have the TCU reflashed with latest software. It may have become corrupt
Presume that the transmission is well maintained? If not - fluid flush & filter.

If a TCU reflash does not solve this - you might have to look at the valve body.

Good luck!

Dingleberry

tcu plug does not leak and it is the revised version. it does it in both modes. trans fluid is fresh and at proper level.

i do notice that the car rarely has these hiccups when its being driven pretty hard, which leads me to believe that it's something the TCU may be doing

splinter

Seems it only afflicts the C32s.

Ridden in and driven many five-speed MBs and AMGs whose lock-up is almost imperceptible.
Several here have had their transmissions/torque converters/TCUs replaced under warranty or out-of-pocket only to suffer the same malady. Could be considered somewhat normal since most tend to do it to varying degrees. Puttering about like a respectable citizen brings out its worst. Flogging it masks the symptoms.

Suspect it’s an incompatibility between the lock-up clutch’s lining material (friction coefficient) and the software programming the timing and severity of the PWM lock-up event itself.

Translation = mine still does it, as I’ve not yet stumbled across the cure.

Dingleberry

my issue sounds a lot like this guy's: https://mbworld.org/forums/c-class-w...eeding-up.html
he's coasting/slowing down 20mph, then gets that annoying lockup when getting back on the throttle..

Dingleberry

thanks for the info.

if you see above, there's an instance of this affecting a c230 as well.

you talk about symptoms, are they exactly like mine? i never ever have any harsh engagement coming off of stoplights at any throttle position like many of the threads i have read.

i've read some posts that jerry's tcu tune makes the trans behave properly. i've also read that the eurocharged high stall torque converter also takes care of these issues, but it might just be a shameless plug from them.

Dingleberry

is it even worthwhile to swing by a shop that has STAR and try to reset adaptations or is that just a waste of time and money? how can i find out if my tcu has the latest software?

Glyn M Ruck

Mr Goodlove squire - My records show no difference in AMG 722.6 mapping. This could well be wrong as it is pretty old MBSA data. I thought, however that C32 spec was locked down a long while back.

Had a blast in a friend's C55 today I'm still smiling!!! That 5 speed behaved exactly as mine does. No percieved slipping. Did or does the C32 have a specific peculiarity in your opinion?

mtnman82

Does the behavior change if you're in 'S' vs. 'W'? If you're on an incline, nose pointed up, at a standstill with foot on the brake: in 'W' mode if you take your foot off the brake the car will stay in the same place; in 'S' mode the car will roll backwards. I believe I read this in the manual, and have tested it in my driveway. I drive around in 'S' mode most of the time becasue I can coast from a greater distance to a stop - better gas mileage ('W' mode will grab and slow the car quicker). Not sure if this is related to the problem or not, just thought I'd mention it...

Nice friend, Glyn! And a nice little Christmas drive, eh ...

Dingleberry

thanks for the input. i'm not sure if any of this related

W203E35

The throttle with the key and engine off AKA "Sneaky ECU Reset' doesn't do crap for the shift. I tested and looked at Adaptation parameters and it doesn't do anything.

Glyn M Ruck

This looks pretty much correct but it has changed from time to time with software upgrades. I wonder which version this was?

splinter

All due respect, Karo, the OP’s 722.6 is markedly different from yours.

Pleased you enjoyed a go in your friend’s C55.
Save for the interior, tinwork and that ~350 horsepower lump under the bonnet, they're almost the same as any other C. ;)

Graph is woefully dated; posted for illustrative purposes only.

The threshold between ‘A’ and ‘C’ is, at times, insufficient in the C32 to avoid an unpleasant jerk when lock-up is triggered.
Doesn’t bother me in the least, but when dilettante passengers ask “what’s wrong with your car?” they’re not to be invited for another ride.
Nah, actually learned how to manipulate the throttle to help minimize its unbecoming effects when friends or clients are aboard.

Installed a $2 manual switch in the GMC’s 4L60 to command lock-up whenever the ECU deems otherwise. It’ll reduce the flexplate/driveshaft rotational differences on the order of 600 rpm depending upon its load/gear/vehicle speed. Useful to help reduce ATF temperature generated from inevitable torque converter inefficiencies, and improve so-called “compression” braking while decelerating. Have seen firsthand how GM had the good sense to include a suitable damper between the output shaft proper and friction surface interfaces – like any pedestrian manual clutch plate – to mitigate abruptness upon engagement.

Don’t have the wherewithal the cut apart my 722.6’s second replacement converter for further examination.

torque converter pictures and stall speed information

Dingleberry

i decided to take a video, forgive the crappy iphone footage...
forgive the CEL, freaking worthless secondary air pump...

video 1: demonstrates the problem, at constant throttle, no problem. i let off the throttle, you see the rpm's drop, then i get back on the throttle and it jerks back down to 1700rpm
http://www.youtube.com/watch?v=OOVcqo1ZeJc


video 2: after some WOT passes, the converter stays locked on decel, as it should. this is absurd that i have to smash the gas pedal to avoid this crap
http://www.youtube.com/watch?v=-LZnzouXa5g

Glyn M Ruck

Wow! very interesting - I've never seen or felt a 722.6 do that. But I have to be fair. I have little experience of the C32 & my friends that owned them have moved on to other vehicles. Splinter & FrankW know these vehicles well on this forum & I would bow to their superior knowledge anyday. TemjinX2 might also be able to tell you what his C32 does.

Your videos are very usefull. I can assure you that what you are seeing has nothing to do with the 1st to 2nd one way clutch that is known to fail - usually at high mileage in taxi service.

I could understand AMG doing a software flash that protected the box from the greater power & torque outputs that it is expected to absorb in the C32 but that would make no sense with what you are showing. Let's encourage John, Frank & Mike to watch your videos & comment.

I would personally still suggest a TCU/ECU reflash but maybe it won't make any difference.

Glyn M Ruck

Yeah sure squire! Not quite an "out of control axe murderer with headlights" C63 (Clarkson). Exhilarating nevertheless after my "sprightly" ahem I mean pedestrian 240.

LILBENZ230

I love that quote from Clarkson about the C63.. spot on. C55 > C63 anyday. Power corrupts, and absolute power corrupts absolutely. 450hp is useless if it can't be controlled.

Dingleberry

i'm sure the dealer will fleece me on this procedure. can any indy shop that has access to STAR do this for me?

mtnman82

Thanks for posting the vid. I'm going on a trip today in the merc and will try the same procedure to see what happens. Looks like you're in 'W'?

Also, please let me know what they say & what the cost is on a re-flash (and if there's any benefit according to the dealer). I've been wondering if there's any better software for the tranny in my car for quite some time now. I woudl imagine with as thorough as Mercedes is, they probably have different software loads for the tranny based on the engine it's mated too (one would hope)?

Also, you might try switching between 'S' and 'W' on an incline (nose pointed up) just to see if things are working from that perspective...

Dingleberry

should i have posted this in the c32 section?

Glyn M Ruck

There are certainly indy shops with STARs - I don't know whether they have access to updated software.