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Hi guys. I am fairly new to the MB gang. I purchased my first beauty, a 2015 GLK 350, a few months ago. This car is awesome. Like freakin awesome. However…
I’d say about a month ago, I started to notice some odd shifting behaviors. This comes in 4 varieties…
1. The most noticeable. The upshift from 4-5 is terrible. I’m talking a jerk that everyone in the car can feel. It feels like I am getting thrown backward, then instantly forward. It almost feels like a momentary lapse in acceleration. Now I will say, it does not happen every time, maybe like 80%. It happens more noticeably in E mode, and it seems to happen more the longer I drive that trip, meaning the transmission is hotter. I have an iCarsoft, which I have used to reset the adaptations, which did help tremendously, but only for about a week, then the issue slowly returns. I am leaning towards software issue for this? Why would resetting the adaptations solve a hardware issue?
2. The downshift from 4-3 sometimes leads to a clunk. Not an audible clunk, but one that I could very easily imagine making a clunking noise. It’s a very different feeling that Problem 1 that I described above. There’s not the “momentary lapse in acceleration” like in the above, but honestly most a really clunky downshift. Resetting adaptations did not seem to fix much for this one, but they do a little.
3. This one is weird. The GLK has 2 shifting modes, S and E. This problem only happens in S mode. Normally, S mode shifts each gear at around 1800-2000 rpm. However, if I even remotely step on the gas, the car will go into this “aggressive mode”, where each gear starting at 3 will only upshift at exactly 2800 rpm. 1st and 2nd seem relatively uneffected, but 3 and 4 and 5 are terrible. I honestly cannot get out of these gears without using the paddle shifters. This “aggressive mode” does not turn off until the car is turned off. I’ve tried switching to manual mode and also E mode, to no avail. Also, this mode persists even after adaptation reset.
4. Finally, I am having some vibrations over about 70 MPH. This one could be a drivetrain issue, as I have not have my tires roadforce balanced. I did have them balanced regularly and an alignment done when I bought the car. I want to bring the vibrations up just in case it can lead to a diagnosis by the wonderful people in this forum, and it seemed to creep up around the same time as the shifting issues did.
Wow, that was a lot to type. The shifting issues seem to me to be software related? I really need some help on this one. I do plan on doing the transmission fluid change at 70,000, and I am currently at 65,000. My plan was to discuss this with the indie shop that I will be going to, but I really want to drop it in here first. Any help is much appreciated!
I do plan on doing the transmission fluid change at 70,000, and I am currently at 65,000.
Why not do it now? Be sure the torque converter is drained in the process, and change the filter. Use the correct fluid, not a "fits all " fluid. Verify, but I think yours probably needs MB 236.17 fluid. Make sure the software is up to date, and reset the adaptations after the fluid change. Then, try driving it in the mode that is giving you problems. Hopefully, it is not a hardware problem.
Why not do it now? Be sure the torque converter is drained in the process, and change the filter. Use the correct fluid, not a "fits all " fluid. Verify, but I think yours probably needs MB 236.17 fluid. Make sure the software is up to date, and reset the adaptations after the fluid change. Then, try driving it in the mode that is giving you problems. Hopefully, it is not a hardware problem.
I am considering just getting this done now. The shop that I am using does use only MB parts, fluids included, and they verified that they can/will flush the torque converter as well. The reason that I wanted to put it in this forum first is because if some of y’all have had issues like this, maybe hardware related issues like solenoids or valve body or conductor plate etc, I can save the cost of flushing the tranny fluid for $500, only to need to reflush when it turns out a solenoid etc is the issue. Just wanted to toss around some thoughts as to what could be going on and hear some of your stories with the GLK.
You used your scanner to reset the adaptations and didn’t mention getting any transmission codes, so can we assume you didn’t get any? It would be unusual to have a hardware problem without trouble codes.
I’m thinking that your shift problems could be transmission fluid that has lost its friction characteristics and a clogged filter. The pan has to come off to change the fluid and the residue in the bottom is a very good diagnostic indicator. If there is anything wrong there, a competent shop will bring it to your attention.
I changed the transmission fluid in my 2015 GLK350 at 60-65k miles and it went trouble free until it was involuntarily retired at 155k miles.
You used your scanner to reset the adaptations and didn’t mention getting any transmission codes, so can we assume you didn’t get any? It would be unusual to have a hardware problem without trouble codes.
I’m thinking that your shift problems could be transmission fluid that has lost its friction characteristics and a clogged filter. The pan has to come off to change the fluid and the residue in the bottom is a very good diagnostic indicator. If there is anything wrong there, a competent shop will bring it to your attention.
I changed the transmission fluid in my 2015 GLK350 at 60-65k miles and it went trouble free until it was involuntarily retired at 155k miles.
You are correct, no codes. The iCarsoft system does have its limitations from what I understand, but it does check for codes in the TCU module and found none.
If the issue had to do with fluid that needed to be changed, then why would resetting the adaptations solve the problem for about a week? That’s what I’m struggling to wrap my head around. I suppose in my head I was including fluid into the “hardware” category, meaning there is physically something wrong down there vs a pure software problem.
You mentioned that you changed your trans fluid at 60-65k. Were you experiencing anything odd that made you do it early?
You just bought a vehicle and have no idea how it was beat up and no idea if it has trans fluid in it !! And no idea if it’s burnt crap, But a month ago it starts acting up bad like it’s going to need a new transmission, but you say “ oh I’ll just wait 5000 more miles to change the fluid” geez wake up. I think you just found out why the last guy sold it.
You just bought a vehicle and have no idea how it was beat up and no idea if it has trans fluid in it !! And no idea if it’s burnt crap, But a month ago it starts acting up bad like it’s going to need a new transmission, but you say “ oh I’ll just wait 5000 more miles to change the fluid” geez wake up. I think you just found out why the last guy sold it.
I wouldn’t say it’s acting like it’s going to need a new transmission…out of all upshifts and downshifts between 7 gears, zero issues other than the 2 described above. Plus there are no codes thrown…
The transmission fluid 100% needs to be changed. Just wanted to throw my symptoms on here to see if anyone experienced anything similar.
I dread experiencing what has happened to you. Have your parts purchased at FCP euro, it’s going to be expensive, just an oil change 500+, and hopefully just rebuild the valve body but who knows.
Is there any clunking from the front when shifting ? You need to check all cv and u joints.
I dread experiencing what has happened to you. Have your parts purchased at FCP euro, it’s going to be expensive, just an oil change 500+, and hopefully just rebuild the valve body but who knows.
Is there any clunking from the front when shifting ? You need to check all cv and u joints.
Yes I was quoted for the oil change at right around $500 including torque converter.
You seem to be leaning towards valve body as being the suspected culprit? Would valve body issues be temporarily resolved by resetting the adaptations like in my case? I did read a thread about the PMW Solenoid being the culprit of a jerky transmission, but the users claimed resetting adaptations didn’t do much.
As far as the clunking, the only time I feel anything like that is the 4-3 downshift that I described above, which happens maybe 20% of the time. It’s fairly rare. It doesn’t feel specifically like it’s coming from the front end, more the mid? Like under my seat ish.
they verified that they can/will flush the torque converter
I'm not a big fan of flushing. Usually it means they're not going to drop the pan and change the filter. The torque converter has a separate drain plug. Make sure they take it out and drain the converter. Also, as Piggy pointed out, changing the filter is a must especially given your issues.
You mentioned that you changed your trans fluid at 60-65k. Were you experiencing anything odd that made you do it early?
No. Just out of caution I was in the habit of changing transmission fluid and filters around 50k miles. 2 highly qualified indie shop owners convinced me that the Mercedes transmissions could go 60k without problems and that’s what I do. Many members here seem to agree with that change interval.
I'm not a big fan of flushing. Usually it means they're not going to drop the pan and change the filter. The torque converter has a separate drain plug. Make sure they take it out and drain the converter. Also, as Piggy pointed out, changing the filter is a must especially given your issues.
I've looked at the process for changing the fluid in the torque converter - doesn't look like a whole lotta fun. FWIW, I've used a very easy, very effective method for doing a "full fluid change" in the past, and it should accomplish the same thing as a "regular" fluid change plus a TC drain...
1) Disconnect the transmission cooler line going to the cooler (or radiator internal "cooler", if that's what your car has)
2) Insert the line into a calibrated container
3) Start the engine long enough for two quarts (liters, if you prefer...) to flow into the calibrated container
4) Add two quarts / liters of fresh fluid
5) Continue until only "new fluid" is flowing out of the cooler line
6) Reconnect the cooler line and top off if necessary
7) While the above will result in getting the fluid level back to where it was, you might want to do the proper procedure to make sure the level is where it SHOULD be... (45°C, IIRC, after shifting through the gears a time or two, just a dribble flowing out the drain hole from the standpipe
Oh inside the trans?
There isn't one on the actual torque converter.
The shop that I will be getting the transmission fluid changed at has assured me that they will be draining the torque converter fluid as well.
After reading through the responses in here, I think the first step is definitely to go ahead with the full fluid and filter change out, resetting the adaptations, and having the software checked out with STAR.
My hope is that this resolves the issues. Would a STAR system be able to diagnose a potential hardware issue? Such as solenoids?
I'm not sure what you mean by a "software issue". Either you have the correct software load, or you don't. It's not like it is self modifying code that made a mistake...
I'm not sure what you mean by a "software issue". Either you have the correct software load, or you don't. It's not like it is self modifying code that made a mistake...
Good point. I guess what I mean by software issues is that most of my issues are temporarily resolved when I reset the adaptations. For about a week, she drives like a dream. That was leading me to think it seems to be an issue on the software/programming side vs a hardware issue. If it was hardware, then wouldn’t the issue be present at all times?
Also, I’ve read some threads about people claiming that a software reflash has resolved some issues, but not sure on the specifics.
Most likely new fluid and filter will make quite the difference, along with adaptations reset as part of the typical tranny (can you even say that?) service.
Suggest you reserve judgement and further wonderings until AFTER service is done
02-05-2024, 08:05 PM
