rawkkrawler

So this seems to be a repeatable issue. 2013 P31 C63. stock tune as far as I know. Manual shift from 2-3 has a little hesitation/slip. Temps are good before experiencing the problem. Doesn’t matter if the the sport/traction control is on or off, happens in any mode. Also can get it during the 1-2 shift as well. Noticed it the first time during a spirited drive, highish RPM’s. Pretty normal under 3k RPM. I hesitate to call it a slip, as it seems to just pause then shift. Side note, oil temp was around 240F. Not unusual for Florida with 85F ambient. Any thoughts?

INS1GNIA

It could just be functioning normal. You can try resetting the TCU (shown below).

• Turn the ignition key to the "on" position which is just before you crank the engine to start.
• Press the accelerator to the floor and hold for 5 seconds.
• Then turn the key to the off position but do not remove the key, then release the accelerator.
• Wait at least 2 minutes, the ECU is then reset.

The TCU reset procedure only erases the adaptive transmission and throttle settings. It does not erase any of the fuel, timing or other programming. Go out and drive afterwards for a bit.

You could always unplug the battery for a while to reset things and then go for a drive and see if anything changes.

rawkkrawler

I’ll try this again, did it once when I bought the car.

Played around with it again this morning. It seems as though if I climb in RPM (not WOT) it shifts smooth and quick in manual mode. Tried manual up shifting at 3k, 4k, up to 6k in all gears, seems normal. If I go WOT, I can get it to hesitate on the 1-2 as well as 2-3 shift, mostly 2-3. It’s a very clear “cut” the delays going into the next gear. So, the only difference between these two scenarios is the kick down button under the gas pedal. Does that button do something with the ECU that could explain the problem?

I’ll do the TCU reset today. Just didn’t thing the reset would effect manual mode.

Thanks!

eightysixtuned

i ask every time someone posts this because its the majority of the time the case. DO YOU HAVE A TUNE?

rawkkrawler

As mentioned above, stock tune from what I know. Going by what the one owner prior told me. I can dig into the forum for the answer, but is there an easy way to know?

eightysixtuned

stock tune, stock vehicle...transmission should last a very very long time. only reason it would slip is if the vehicle was heavily tracked and fluids and filters were never maintained. race duty will cause fluids to deteriorate quickly.

rawkkrawler

I agree. Slip might not have been accurate as it implies the RPM’s stay consistent. It’s more of a hesitation, like power disappears for a second. Still snaps into hear just as hard, just not 100 milliseconds. Enough hesitation to create a jerking sensation. I personally changed the trans fluid 100 miles ago. Clean coming out.

INS1GNIA

When shifting in manual, there is a slight pause/loftyness/float/delay. I want to say that this maybe what you are describing. Totally normal, a tune can make it a little less noticeable if needed.

rawkkrawler

Sounds like what I'm feeling. It's strange that it only happens at WOT. With the RPM's climbing, without the pedal to the floor, and at any RPM, it snaps into every gear as expected. It's when at WOT that it acts up, mostly on the 2-3 upshift, and sometimes on the 1-2. Unfortunate that this could be considered normal with a C63. But as I've read plenty of times, there's a love/hate relationship with the MCT.

I'll be working with Barry soon.

rawkkrawler

Felt the need to give a quick update, hoping it might help anyone servicing their own MCT.

Every step was followed precisely to change the fluid, including dropping the pan, replacing the filter, replacing the gasket, replacing the bolts, etc…

Here’s where I went wrong. I don’t own the computer/scanner to check for the 113F temp when refilling. I used an IR thermometer and assumed I was close, guess not. When I added the extra fluid, and let it drain to self level, I buttoned it up. Shifted fine with “normal” driving. Only felt the hesitation when adding a little more throttle. Went ahead and removed the drain plug this weekend, about a cup drained out. Pushed about 2 quarts back in, got it up to temp and shifted between P,N, and R. Then, I let the fluid drain. One of the two quarts came out this time. I estimate about a quart low. Took it for a proper test drive, shifts perfect!

Boneheaded move on my part, but wanted to close out this thread with what I found. I imagine this could happen to anyone if they don’t know the temp of the trans when doing this service. Hope this helps. And as always, I appreciate all of the great suggestions/responses.