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· *Registered
2009 SLK55 AMG w/P30
1,877 Posts
Gentlemen, I'm pretty sure I'd know if my shift lever was in neutral. Especially so if I had just passed some slow dolt on a busy highway. Enough of the "operator error" chat. I would agree to tech problems if the hesitation dropping revs after full throttle lasted more than a few seconds; mine never has. I just consider it to be some (probably-retired-now) engineer's whoopee cushion for us. As long as it isn't a surprise at a bad time.
Who suggested you hit neutral? I don‘t see that.
On the other hand, my bet everyone of us who commented or raised a question can tell you it has happened to us that we accidentally downshifted or we forgot that we downshifted and failed to upshift. The 7G gearbox is pretty reliable in my experience so set aside your indignation that we may have suggested you made an error and tell us when you last had your trans serviced. Have you run a scan for any error codes? Someone suggested you try recreate it. Have you done that?
Folks are just trying to help mate. No need to get bent.

· *Premium Member
2007 SLK280
273 Posts
Totally understand. Not bent at all. Apologies if I sounded that way. Just a trait I've noticed and accepted as part of the nature of the 280 breed since I bought the car 15 years ago. No paddles on mine to tempt me and that's probably a good thing. I stepped in only to say I've often experienced a delay (brief) in rev drop after flat-out expressed in the initial post and I didn't see it as unusual. End of story.

· Administrator (Canada)
24,849 Posts
If I could offer an off-make example:

My F150 has a 10 speed tranny with 375 HP so no slouch and with 3 options to choose from :

1)'standard (default--similar to "C" in SLK which starts in 2nd) -- shifts from 1=3=5
2) eco (wont' go there but similar skipping of gears, still like our C mode--but worse) and
3) sport (like our sport) ie: no skipping of gears.
4)even have a manual mode but irrelevant here (so four gear selection options)

If I'm on the highway and floor it in any mode (except M) , she drops down to say 5th from 10th. I let up and it hangs in 5th with the corresponding high revs for at least 3-4 seconds.

From what I've read, it's "expecting" (ie software programming) you to continue in 5th (my truck) and once it "realizes" it's not gonna happen, shift changes up and revs drop.

Now, I don't remember if that analogy can apply here BUT it seems quite likely.

· *Registered
2008 SLK350
251 Posts
Hi all

So the other day I was driving home and some guy behind was being....... "one of those".... so at the appropriate time, I floored it and I noticed after releasing the pedal the RPMs dropped from the sort of 7-9k whatever it is down to 4k and remained there even though I was now driving normally. It hasn't done it since... but has made me wonder why that occured and I haven't gone to those kind of speeds since as bit concerned what that was... it hasn't done that before.

Any thoughts?
Maybe my English is not good enough for some subtleties... I read all two pages and I'm still not clear about what happened.

Briefing those two pages:
So you used the kick-down, which makes the car going to the shortest gear (certainly not anywhere near the 7-9k range since your engine doesn't get that up, but understood: near the red line) and kept accelerating. Once the situation cleared off, you released the gas pedal. The gearbox upshifted like two~three gears (depending on your current speed) so it reached about 4000RPMs and then it stabilished there even given you completely left the gas pedal alone and it stayed that way for about a minute.

So the first thing I want clarified is: in your first message you said "remained there (at about 4k RPM) even though I was now driving normally", but then you said afterwards "all I was doing was coasting along, no pedals pressed". That makes a huge difference, so what was it? Were you driving "normally" as in "not spirited" or did you take your foot totally out of the gas pedal?

You later on even said "the engine was truly reving at that 4k speed it wasn't just the gauge. But, it was like the car was in neutral as the car wasn't actualy trying to "drive" it was just coasting"". I don't get what this exactly means either.

If your engine really was in neutral (just let's imagine for a moment it used a manual gearbox), of course the engine could be at whatever RPMs as you pressed the gas pedal (or else, in case of gas pedal failure, at whatever the electronics "thought" you were pressing the gas pedal), but the speed would be slowly going down (as no engine would be pushing the wheels but nothing would be braking it either). So, was the speed in that situation slowly going down, as if truly in neutral, somehow quickly going down, as when the gas pedal is not pressed and the car is slowering down due to engine brake, or was it sustaining its current speed as if you were just gently pressing the gas pedal just for the speed to be maintained?

Now, while I wait for your answers to my questions above, I'll advance what I think it's the most plausible explanation (unless your answers point somewhere else).

Let's forget for a moment about the engine's RPMs, and let's focus only on the gas pedal: you quick-downed, went accelerating for a while and then you released the gas pedal, also for a while, till you reached your desired cruising speed again, then you gently pressed gas pedal as to maintain your current speed. Like when overtaking on, say, a 100kph-limited road: quick down for overtaking, let's say the car goes up to 140kph, and once the overtaking is finished I just let the car go, so it speeds down, and once back at 100kph, I press the gas pedal just enough to sustain those 100kph. Is that it?

If the case was the one I painted above, then I'd say everything was normal with the only minor caveat that, yes, sorry, there's a bit of "operator error" as you said, going there. Not really operator error but just that your "full minute" wasn't that much but just about 15 seconds to half minute and it just seemed to you much longer. Otherwise, depending on the exact answers to my questions above, I'd look towards gas pedal malfunction or gearbox' conductor plate failure early symptoms.

PS: now that I think of it, was the cruise control activated?

· *Administrator (Premium Member)
45,458 Posts
One other check.
Make sure it is properly in place.
They can come loose under the pedal and foul brake/accelerator.
They can settle back into place for a long time and then do it again.

Also, perhaps a stone fell loose from footwear and fouled something but then fell out of they way.
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