One behaviour I noticed on my AMG GT is that it never seems to skip gears when downshifting. If I’m cruising along in auto mode in 6th or 7th gear, and then I suddenly floor the accelerator, the car acts confused and lethargic for nearly two seconds fumbling down to 5th, 4th, 3rd, and finally 2nd gear to actually accelerate, and then it starts giving full engine power.

Why can’t it skip gears when downshifting? Is this normal? I hate this behaviour - when I kick down, I expect it to shift straight into the gear for optimal acceleration (or at least the gear above it if the optimal gear is on the same side of the transmission it’s currently on). My old BMW M240i with the ZF 8-speed would shift straight to the optimal gear when I kicked down. So does my CL63 (though a little slow in shifting), and so do most cheap rental cars such as a Kia Sportage I drove a while back.

I don’t have my much experience with other dual clutches, but I did drive a Porsche PDK a couple times and don’t recall having this complaint.

 

What driving mode see you in? I assume you are switching the driving mode to manual.

i don’t have this issue. When driving daily I have the car in race mode or sport+ - esp off or in sport esp mode. If off I leave the traction knob at half way.

In these modes the shifting is crisp and precise.

 

Manual shifts are crisp and precise. The only problem when shifting manually is I need to pull the paddle 5 times to go form 7th to 2nd, and while the first manual shift is quick, subsequent ones are slower as the gears need to move.

The problem I described is worst in comfort mode auto (where it picks the highest gear whenever possible). In sportier modes, it picks lower gears for cruising, so there are fewer gears to downshift.

In race mode, this isn’t an issue because it just stays in low gears, and doesn’t need to downshift much. Right now, what I do when I want to accelerate out of the blue is switch to race mode (so it downshifts in advance), then floor it. However, it would be nice if it could kick down quickly from comfort or sport auto modes, like most other cars with conventional auto transmissions.

 

I think that if you press and hold the downshift paddle for a second it'll skip to the lowest gear it can

 

This is a function of any DCT box. The next gear is tee'd up on the other shaft of the gear box. If you're cruising the car will assume that the next gear will be a higher one so that higher gear is ready.

When down shifting aggressively you can hold the down paddle rather than pull it multiple times. The car should then go into the lowest appropriate gear.

To be honest cruising along and then randomly nailing it isn't rally something I do so this hasn't really happened to me at all.

 

That's the nature of a dual clutch transmission and stems from its mechanical limitations. They all do that at various degrees, even the PDK. DCTs are only fast if the next gear has already been correctly pre-selected on the other shaft, then the shift is just a matter of opening the current clutch and simultaneously closing the other clutch. However, if the next gear is not the one that was pre-selected or even worse if the next gear is on the current shaft, then things are fairly slow, because of the need to move the sleeves and the required gear synchronization for a successful mesh. Under the covers, a dual clutch transmission is essentially two computer operated manual transmissions and by themselves, due to the gear synchronization needs, they don't shift all that fast. The way DCTs accomplish the fast shifts is as described above, by making the next gear selection before it's needed so the time it takes to shift gears is disguised. DCTs are not designed for mutli gear changes. They are designed for fast sequential gear changes.

Automatic transmissions use a planetary gear set which uses several clutches and bands to accomplish a gear change. There is no need for synchronization or meshing gears. It's just a matter of opening/closing one or more clutches and/or bands, so a shift from any gear to any other gear takes the same amount of time as a single sequential shift. AMG for example uses what they call a multi clutch technology transmission in most of their other models, and especially the latest 9-Speed MCT while it doesn't shift quite as fast sequentially as a DCT, it makes up for it by being much faster on multi gear shifts. The MCT is essentially a regular planetary gear automatic transmission at the core, but instead of a torque converter it uses a wet startup clutch, so it kinda combines the benefits of a planetary gear transmission with the benefits of a DCT, such as more responsive drivetrain via clutch instead of fluid coupling.

As much as I liked my DCTs in the past, the MCT actually is overall better for street driving, where the gear changes aren't as predictable as on the race track. The best experience with a DCT is if you manually shift into the correct gear and then accelerate, just like one would do with a traditional manual transmission. You can press and hold the downshift paddle to quickly downshift to the lowest possible gear for maximum acceleration and then step on the throttle. This still take 1-2 seconds, though until it registers what you wanna do and execute the shift. Overall the best strategy is to shift yourself and keep it in the low gears, so you never have to downshift more than 2 gears at a time. A two gear downshift can be accomplished by quickly pressing the downshift paddle twice in succession, then it should downshift two gears in one blip.

 

I dislike holding the paddle on my Huracan let's say if I'm in fifth and it drops down to 2nd almost near redline then I have to shift right away. I prefer to just shift the paddles manually. This way I'm always where I want to be. Driving an MCT this way for street driving the shifts are just too slow/lethargic to me compared to a DCT.

 

I drove an R8 for a while and same thing there. That's the nature of a high-revving naturally aspirated engine that makes the power with revs, so for max acceleration you are essentially pegging the redline.

As for the MCT, the 7 speed you have in your C63 has a terrible manual mode. I know exactly what you are talking about. It doesn't lend itself for this kind of driving and coming from a DCT it was one of the main reasons I passed on the pre-FL C63. It's a very different ball game with the new 9 speed MCT. It finally is responsive and shifts properly in manual mode, so you can drive it the same way. Just like with a DCT, the gear changes are now executed the moment you press the shift paddles. The old MCT was laggy and had unpredictable delays.

 

An excellent work-around is to drive the car in ‘D’ in whichever ‘sporty’ mode you choose, and then just manually initiate a single, or multiple downshifts by pulling the left paddle once, or continuing to pull/hold it until the gearbox is in the lowest acceptable gear. You then can just drive out of the corner without worrying where in the rpm band you’re in as the gearbox will just shift up since you are still actually in ‘D’. This is an extremely fast way to attack corners and does not unsettle the car in the least little bit.

I am talking about the DCT in the GT cars though, YMMV in the Huracan.
Bish

 

Have you tried holding the downshift paddle to reach the optimal gear? It did eventually get there, but it was a slow process downshifting through all the gears, maybe 2 downshifts per second. What prevents it detecting the paddle being held, and skipping straight to the lowest safe gear on the unused shaft, rather than working its way down? For example, suppose you’re in 6th gear, and want to reach 2nd gear, why can’t it go to 5th initially, then go straight to second on the opposite shaft when held instead of 6/5/4/3/2?

 

Not specifically in the GT to be honest, but this is not how it's supposed to work. It's supposed to downshift one gear immediately and then if you keep holding it about a second later it should jump down directly to the optimal gear. Some cars have a switch at the end of the throttle pedal and if that switch gets triggered it downshifts to the optimal gear. Similar to the kickdown in automatic mode, but as far as I know AMG doesn't use this method. Some transmissions require you to be on the throttle for this. Try stepping on the throttle simultaneously with pressing and holding the downshift paddle. I have to do that in my C63S if I wanna quickly downshift two gears for example. If I do it off throttle and rapidly press the downshift paddle twice, it goes down one gear and then another and the whole thing takes like a second or two, however if I quickly press the downshift paddle twice in rapid order as I get on the throttle then it immediately jumps down two gears. However, I can stay off the throttle press and hold the downshift paddle and it goes down one gear and a second later jumps down all the way to the optimal gear and that's how it worked on other cars I've driven in the past. I've only driven the GT S and GT R on the track, where one doesn't really use this method.

 

Thanks, jumping down to the optimal gear after holding the paddle for a second is what I expected too. I’ll try applying some throttle and see if that changes anything. It’ll be a month or two before I can test it though as it’s mid winter here .

 

I did some reading of the owners manual. It mentioned that holding the downshift paddle should downshift to the optimal geat for maximum acceleration. However, it only mentioned this in the section for full manual mode (not temporary manual override of auto mode). It also seemed there might be similar functionality in race mode, but it wasn't obvious. The manual didn't explicitly say it will shift quickly and skip gears to do this, but I assume this is what it meant. When I was trying the hold down the downshift paddle, I was in regular sport or sport plus mode with auto shifting, so maybe this is why it was downshifting slowly through all the gears rather than going direct to the optimal gear. I'm eager to try this out in spring once the weather improves.

I also read that there is indeed a kickdown feature that is supposed to downshift to the optimal gear for maximum acceleration, regardless of which drive mode you're in. As usual, activating it requires pressing the accelerator pedal all the way, and then some more. I wonder if I wasn't pushing the pedal down hard enough to activate kickdown when I was fooling around last year.

Accelerating hard all of a sudden after a period of relaxed crusing is not something one would do in normal driving, but I sometimes do it for giggles on an empty strech of road when I want to briefly enjoy the power without continuously breaking the speed limit. It's also my way of judging the responsiveness of the transmission.

I'm particularly sensitive to how quickly a transmission downshifts after a period of sedate driving due to my experience owning a 2012 Ford Focus with a DCT during my student days. It was an absolutely atrocious transmission; it had clutch slipping problems and made grinding noises (improved after various recalls done on it), but also abysmal performance. Manual shifts were very slow (taking close to a second) regardless of whether I was upshifting or downshifting. Also, it was slow to downshift when you floored the pedal, and didn't like downshifting even when slowing down for a turn and then accelerating after the turn. It followed the principle that it's better to lug the motor at 1400 RPM than to downshift, and if you floor it, it should wait 2+ seconds before downshifting. At least it was tolerable in sport mode.

 

I think you found and answered your question. You do need to mash the pedal hard for it to kick down all the way. You most likely weren't doing this as you suggested. Hopefully you get a nice day where you can take the car out sooner than later.

 

Oh, I was fully assuming that you are in full manual mode when doing this. The temporary manual mode when just using the paddles is just a way to temporarily hold gears. It functions very differently from the full manual mode. For example in full manual mode it doesn't upshift automatically at redline, whereas it does in the temporary manual mode. I rarely just use the paddles while still in automatic mode. If I wanna use the paddles I pretty much always go to full manual mode first. I even have my Individual mode setup to put the transmission in M and I use that mode on the highway.

 

I had a 2007 BMW M6 which had an SMG transmission. That transmission was atrocious and BMW finally replaced it with a DCT transmission. I had that transmission in an M4 and it was a lot better. The transmission in the GT is excellent, and in locked shift mode it will downshift so quickly to the lowest gear for maximum torque that it feels like it is not going through all of the gears. The SMG used to hesitate at low speeds and prohibited the M6 from being a DD. Not so with the GT.

 

I managed to take the car out for a short drive today (clear roads today), and confirmed that it does skip gears when downshifting by holding the paddle, in full manual mode at least. For example, holding the paddle while in 6th, it instantly shifted to 5th, then half a second later it went straight to second as I wanted.

However, it doesn’t skip unless you’re already pressing the accelerator some amount to accelerate. If you just hold the downshift paddle while cruising with little throttle, it slowly downshifts sequentially through all the gears.

 

It’s also a function of which mode you’re in AND how dynamically you’ve been driving the car.

 

Makes sense. I was in Sport Plus when I tried it out today FWIW.