uurfantasy

I think I am having an issue with my car downshifting when I want it to go fast. If lets say I am 3rd gear just cruising, and then I mash down on the gas pedal in sport mode, the tranny wont downshift and will jus remain in the same gear and slowly pick up speed. There used to be a time when my car would like be capable of downshifting twice when I mash on the gas. What could it be? I had a ecu reflash done and IC pump replaced a week ago from the dealer. Temp gauge seems fine and SC doesn't shut off, the car just wont downshift and pull really hard like it used to. I even did the gas pedal key in ignition reset as well. Nothing changed. What could it be? Thanks guys!

bfnnrgn

Both of my cars do that. It's very annoying. One of the downsides of an automatic. If you don't drive them aggressively all the time they're prone to do that among other things, I wish the tranny had more agressive settings available and didn't do so much 'learning'. In fact I drive my SLK so sedately sometimes that even at WOT in D it will upshift at 5k rpm instead of going further. I have to select a gear in S before it will shift near redline. It's very frustrating when you want to go go go...

On another note, once before when my E55 was having that issue very frequently the tranny disengaged on the highway and even though I was in D there was no power to the wheels. The transmission valve body had to be replaced. If it concerns you then you might consider having that checked out.

uurfantasy

so i should maybe reset the ecu again using the gas pedal hold with ignition key trick and start driving aggressive, so the tranny can once again "learn" my driving. Thanks!

bfnnrgn

You might consider a sprint booster as well. That helps with the agressiveness since it gives more throttle input with less movement. It helps fool the computer into thinking you drive more aggressively than you are and keep the bad learning habbits to a minumum.

Cosm

I noticed the same thing also, sometimes the car feels fast as hell and pulls like crazy, other times it just revs and does not have too much pull. I wonder if this might help

https://mbworld.org/forums/w211-amg/193233-speedshift-anyone.html

Jakpro1

Sounds like the "load limit limp mode" my car had when I was throwing belts. Cept I would get the error on the screen to visit shop.

You have any messages come up at all with it?

2 Things you can try.

1) Try the ECU reset. Search under Sneaky ECU and you'll find it. After a few years, I think we figured out it really reset tranny shift patterns.

2) Try resynching the tranny by doing this. Put the car in m mode and find long stretch of road that you could coast to a stop on. Get the car up in 4th gear and get going about 60mph and then just let her coast to a near dead stop. Can't touch the gas or brake at all til near dead stop. Not sure what happens, but my tech (who is SLR trained and runs the Benz shop) does it to all his cars with tranny issues.

Worth a shot.

Keep up posted.

slacker55

I'm not sure if this is off topic, but my car seems to experience shifting problems when upshifting. I'm not sure if it's normal, but it shifts fine when I'm driving normally and going easy on the throttle...but when I really gas it hard to over 5K rpm, and upshift from 2nd to 3rd or 3rd to 4th, it often stays in the lower gear and refuses to shift into the gear I selected until I redline. If I gas it hard to 5500rpm, let go of the gas, and upshift, it would often just cruise on that gear and there would be a 10 second delay before it actually shifts into the correct gear. This only happens in S mode and C mode. I've never had this problem shifting in M mode (not yet at least). I also just had my tranny rebuilt by the dealer. Does anyone have any idea whether this is normal of whether there's a problem? Thanks.

ItalianStallion

Yeah, I think that your tranny is holding the gear because its anticipating a turn or that you are gonna need to jump on the gas again. If you kept going and it hit redline it should shift. But if you are before redline it will hold the gear for a few seconds. It only happens if you are running it very hard. In manual mode, you can totally control the shifting, in D (S or C) mode you can only force the car to downshift, not upshift.

uurfantasy

So I am not getting any sort of message on my screen. So I assume things should be okay. I did the sneaky reset, same thing. If I am in like fourth gear at about 2-3-4k rpms and I completely floor the car, it will stay in that same exact gear and very very slowly accelerate without downshifting at all. But if I use the shifter and downshift, everything works fine. Also, I can't use manual mode because my supercharger doesn't work in manual mode at all. I need to take it to a dealer but just too lazy since I never use manual mode anyways. What could be causing supercharger to not work in manual mode?

Cosm

I wish my car would do that all the time !! it does it sometimes and I can feel the power ready to go but if you don't like it just hit the upshift 2 times on the shifter and it will go into the correct gear for cruising. I beleive that the car is just waiting to deliver the power you want especially if you drove it hard which is what I am trying to get my car to do all the time !!!

johnny_b

Old thread has this been solved have a similar issue car does not like to downshift

Crissus

On the C215, W220 its the gas pedal. Happens on my car aswell when crusinng around and quickly flooring it, it stays in gear 50% of the time. Playing then with the pedal up/down and suddenly it shifts down a properly accelerates.

BoostedAero

Try the "Sneaky ECU reset" and see if that helps at all more than likely adaptations have been made to cruise around...

*Being in "Sport" mode also will change the way the transmission reacts. It will hold gears longer and anticipate acceleration by downshifting earlier*

I do not think the TCU adapts to driving styles or holds data, perhaps others can chime in. The only adaptations I know of in the trans are for actual clutch pack filling pressures.

ECU reset:

1. Turn the ignition key to the on (not start) position.

2. Press the gas pedal to the floor and hold for five seconds.

3. Turn the key to the "off" position (don't remove the key), then release the gas pedal.

4. Wait at least two minutes for ECU to reset.

GinDistiller

I'm reviving this thread a little bit as I've been having some odd issues and need clarification on reset data. I've searched and it seems there is no official conclusion as to the Sneaky reset or unhooking the battery overnight...do either of these actually clear out old codes in the TCU and reset adaptation values or can that only be done through STAR?

Long story on what I did with my tranny, but at one point the valve body had a shift kit installed (bad idea btw) and car was going into limp mode etc so I'm sure set a bunch of codes in the TCU. In fact the shop may have even keyed on to roll the car out of a bay while the valve body was removed for the steering lock. I reset the main codes with my MBII scanner, but I don't have a STAR to look at the specific ones. I've since reinstalled all stock, known, working components inside the transmission/valve body, and installed a new conductor plate. No codes showing at all now.

Car is now completely driveable, makes great power, but is constantly in too high of a gear and not downshifting quickly. I mean, it shifts into 4th at under 30 mph and so when I give it 30% throttle the whole car bogs down because I'm around 1k rpms. If it give it assertive gas it will downshift and off I go, but I can only drive it slow or quite fast now, so traffic is a bear.

Is this just normal for these transmissions and fuel economy reasons? I have the same 722.6 trans in my Jeep and it seems to keep the car at 1500 rpm at a minimum most of the time, which is much better, but the gearing is completely different in that car.

Wondering if it's worth bothering someone with a STAR to go in and force adaptation reset, or if I can rule this out having done the Sneaky ECU reset as well as an overnight battery disconnect.