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Discussion Starter · #1 ·
Have you guys experienced a longer than mercedes-usual reverse engagement, when you are trying to do a 3 way turn? Like almost 2 seconds?
 

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Have you guys experienced a longer than mercedes-usual reverse engagement, when you are trying to do a 3 way turn? Like almost 2 seconds?
I would rush that at your own peril

all the gremlin storis are about the tranny, and reverse

I put it in reverse only at a full stop



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with brake fully pressed

and first thing in the am, I let the clutch packs fill at idle until it rolls by itself. new,40 deg ish, like 6~7 sec
that little quirk is worrisome by itself




Yes, its total sheisse to be terrifieed of some pin or spline shitting the bed, yes it makes parking and close quarter manuevering a life sapping chore.
but it is what it is
 

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Discussion Starter · #3 ·
Ok, I had seen that on a cold morning, it can take really long time time for the car to get going.

And this is my 5th Mercedes and all the other ones were slow to engage reverse from drive, like when you park or do a 3 way turn. This is just even slower.

And I did have hopes that with the new technology and low miles, I may get quick-er response.

But ok, I’m not looking to break the gearbox, thanks.
 

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I have trouble some times but it is my own fault. If the brake isn't adequately depressed reverse is forbidden. I know it's on me because the back up camera does not activate.

But if the camera is on and the transmission isn't responding and the car is warmed up then that is something else. How many miles since you're your last transmission service?
 

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Have you guys experienced a longer than mercedes-usual reverse engagement, when you are trying to do a 3 way turn? Like almost 2 seconds?
Yes.

I also get long engagement times when slowing for a turn. Like, slow to 20 MPH as I approach the turn, then try to accelerate out but it take ages for the clutch to let out while I just coast there on the gas. The RPM is there, the power is there, the gear is there, but the clutch just decides to do it's own ho-hum thing and get there when it gets there.
 

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Based on the way you are driving like speeding up the car is preparing for the next shift up with the dual-clutch. If you are in the mode of speeding up and then suddenly slow down then the car needs time to readjust from speeding up to slowing down. The example of slowing down on entering a curve and then hitting the gas to speed up happens as the car is preparing to downshift as that is the way it sees things coming up and you hit the gas and it was not prepared for the upshift. Think of it as the car sees you speeding up so it prepares the second clutch and gear to take over for a smooth fast shift or you are slowing down and again the second clutch and gears are preparing for another downshift A sudden change to the opposite take time to change. Dual-clutch has one clutch for odd number gears and second clutch for even number gears and reverse on just one of the clutches.
 

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Good point on the shift preparation. I believe reverse is on the same shaft as first. So rather than one clutch disengaging and the other engaging to shift to the next gear the controller has to disengage the clutch, change the gear, verify the change was successful, and then engage the clutch. If the oil isn't moving completely this will take longer.
 

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Yes and additionally most DCT's sit idle at stop with the primary clutch in 2nd gear as the computer doesn't know whether you will next go forward or reverse. So that too takes some time. DCT's are marvelous on the track but in day to day use the ol' slush box is still superior. That is why many manufacturers are going back to same on non-Sport models. But saying that, even the latest Mini JCW GP now has a traditional 8-speed auto trans, and it's definitely a sport-track machine @300Hp.
Good point on the shift preparation. I believe reverse is on the same shaft as first. So rather than one clutch disengaging and the other engaging to shift to the next gear the controller has to disengage the clutch, change the gear, verify the change was successful, and then engage the clutch. If the oil isn't moving completely this will take longer.
 

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Discussion Starter · #9 ·
So then, this is normal behavior:

As the gearbox oil is cold or very cold (say outside temp is in the 40s F), you put it in first gear and ..... want to cross the busy street into Dunkin Donuts. You wait in D (eco off), see and opening, step on it, nothing happens.
Step again on it , nothing happens.
Step third time, it starts to slowly engage. But if you don't watch it, 1 second later (in C mode) if still floored, it would leap forward.
You want to then park it at Dunkin, put it in reverse, nothing happens (although selector confirms R and reverse camera turns on).
You quickly step on it again, this time slightly slower, it starts to move in reverse and 0.5 seconds later, if still floored, it would leap backwards.
By the time I come back from Dunkin (car did not idle parked meanwhile) and leave to cross busy street, it starts to almost be acceptable. I floor it in D and picks up in like 0.5 seconds later. Then at the first traffic light later, it picks up as soon as you step on it, but sluggish and at the second light it picks up normal.

Does my story reflect what you guys see? Is this life with a Dual Clutch?
 

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So then, this is normal behavior:

As the gearbox oil is cold or very cold (say outside temp is in the 40s F), you put it in first gear and ..... want to cross the busy street into Dunkin Donuts. You wait in D (eco off), see and opening, step on it, nothing happens.
Step again on it , nothing happens.
Step third time, it starts to slowly engage. But if you don't watch it, 1 second later (in C mode) if still floored, it would leap forward.
You want to then park it at Dunkin, put it in reverse, nothing happens (although selector confirms R and reverse camera turns on).
You quickly step on it again, this time slightly slower, it starts to move in reverse and 0.5 seconds later, if still floored, it would leap backwards.
By the time I come back from Dunkin (car did not idle parked meanwhile) and leave to cross busy street, it starts to almost be acceptable. I floor it in D and picks up in like 0.5 seconds later. Then at the first traffic light later, it picks up as soon as you step on it, but sluggish and at the second light it picks up normal.

Does my story reflect what you guys see? Is this life with a Dual Clutch?

You might try doing a transmission reset, it can improve pedal response for transmission response. Reset Transmission Adaptive Learning Padel Travel
 

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I believe reverse is on the same shaft as first.
The DCT is really two ‘sub-transmissions’.. reverse actually uses both.. that is why you can get a ‘reversing not possible’ message but still be able to have limited driving and limp it for service.

The 7G-DCT that is used in the 45 isn’t really that far off of what is used in some of the higher end cars like the GT, it’s a strong transmission. Although there’s enough documented failures that say otherwise, this is a forum that’s especially geared (no pun intended lol) towards people posting with failures/problems/headaches with the car versus ‘car-talk’ these days.

I’ve always thought the transmission was a strong point in both 45’s I’ve owned, and had both transmission codes.. 15 and 16. It doesn’t like stop and go traffic, hates it actually.. it doesn’t even really like ‘normal suburbia’ type of traffic.. now it doesn’t fault or anything in this type of situation.. but it can be a little sluggish off the start, a little jerky on a downshift or upshift.. but then get it out where it wants to be and wind it up and push it a little bit and the shifts are so smooth and flawless. I really encourage someone who just street drives this car to go do an autocross event or better yet a novice school or something that will be still be relatively safe for the car vs tracking, because this thing can be pushed really hard, loves it, and was designed to do it.

The key to keeping the transmission running strong and faultless over a long time, as with all mechanical things, is preventative maintenance. It’s a strong transmission, but shifts can be affected by as little as 50mL of fluid discrepancy, so you really need to have this thing serviced by a very reputable service center be it the dealer or an indi, and when a 45 owner hears that the trans service is $500, there’s a tendency to shop around for cheaper, or even go DIY route bc they can’t justify that amount on service for their sub $50k vehicle when the GTR owner doesn’t blink an eye at that service for his $150k AMG and will more likely pay top dollar and search out the most reputable guy.
 

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Let's also be reminded that the "automatic" in a DCT application is more properly described as a "computer controlled dual clutch Manual transmission." As such it heavily relies on the computer anticipating our all too human needs/whims. For example, if you suddenly floor it while decelerating-rolling in a "California stop" it will get totally confused and need a couple seconds to sort things out and align gears more appropriately. Again, not so good for daily driving. In my prior Audi TTS most often I left the DCT transmission in truly manual-flappy paddle control to avoid just such a circumstance (fortunately the computer still wouldn't let me overrev a particular gear, 'manual' or not 😉 )
 

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of course on the track that is EXACTLY how you roll. Brake hard into a tight turn, followed by gassing it immediately as needed to control weight distribution up to and including punching it and getting.....fizzles while the transmission is trying to figure out what to do.

And this has nothing to do with changing gears, as the gear doesn't change. It's just not applying the power to the wheels, even though the car gear is selected and revs are in the right range.

And can't pre-empt it by gassing early because the brakes are on hard a moment earlier. And can't toe heel because if you've ever tried it, you know the GLA won't apply power when the brake pedal is depressed.
 

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Another very basic way of conceptualizing a DCT is a 10-speed bike. The two main sprockets are the dual clutches. The derailleur and thereby gears are controlled by your own brain-computer. Even then I too sometimes get confused. ;)
 

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Another very basic way of conceptualizing a DCT is a 10-speed bike. The two main sprockets are the dual clutches. The derailleur and thereby gears are controlled by your own brain-computer. Even then I too sometimes get confused. ;)
Great way to describe the dual-clutch and transmission.

It is a long way different than a torque converter and an automatic transmission. More like a manual transmission and auto clutch.
 
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