Modern state of (mainstream) single-clutch AMTs: How quick are they to shift gears?
Posted by Final-Mammoth2415@reddit | askcarguys | View on Reddit | 21 comments
I have an Alfa Romeo 156 Selespeed, and contrary to how most people would think, I like the way it drives and feels.
The common criticism on the 2000-2010-maybe 2015 AMTs was that they were slow to shift gears, characterized by the head-nod, as people describe. I am wondering if modern ones are better at this due to advancement in control hardware/software or better electrovalves (for electrohydraulic units), or as the industry simply abandoned single clutch AMTs in favor of DCTs and torque-converter based units, 700ms-1s shift time still is the norm for an AMT in a mainstream car.
I'm being careful by saying "mainstream". :) I know there were single-clutch AMT systems much faster than the numbers I quoted; but Ferraris, BMW Ms with SMGs, or Lexus LFAs are something else entirely.
ScaryfatkidGT@reddit
The issue with AMT and DCT’s is slow speed maneuvers, parking etc, they are jerky and when they grab is unpredictable compared to a a torque converter… torque converted transmission started shifting faster and faster and lose less power than they use to to the point everyone just went back to them…
Try and parallel park a M3 AMT, Alfa Romeo 4C, LFA or a E60 M5 and you will see
The_Coalition@reddit
DCTs are really a hit or miss, depending on the manufacturer, clutch wear and whether it uses a wet or dry clutch. In a Skoda with a dry clutch DSG, I didn't have any major problems regarding low speed driving, but resetting the TCU's memory every once in a while helped a ton. In a Renault Megane with a dry clutch also, it was horrible compared to the Skoda. Meanwhile, a Ford S-Max with a wet clutch PowerShift (which I'm pretty sure is actually made by Getrag, not Ford) drove much smoother than both of them. None of these came even close to a Mercedes 7-speed or 9-speed torque converter though:)
ScaryfatkidGT@reddit
Yeah, wets are better but like I said… all the manufacturers kind of realized for mass appeal they needed to go back to torque converters… someone buying a LFA or EVO is willing to deal with it, but not the M5… apparently the Renault Megane etc
The_Coalition@reddit
my personal ranking would be AMT < older TC < dry DCT <<< wet DCT < locking TC. Apparently, there are also some hybrids (Mazda CX-60, CX-80 and CX-90, if I'm not mistaken) that use a hydraulic multi-plate clutch instead of a torque converter, with the same planetary-gear transmission that would normally be coupled with a locking torque converter. It makes sense to do that, since an electric motor basically eliminates the need for a torque converter at all. Modern torque converters often remain locked up even during gear shifts anyway.
ScaryfatkidGT@reddit
I guess I don’t really care as long as the software lets me fully control it… which is rare… VW’s DCT was/is infuriating
Final-Mammoth2415@reddit (OP)
I think that should be fixable with creep function, at least in the way it is with DCTs. Not as good as the torque converter but for most conditions tho, I believe, but then again DCTs also have issues with similar maneuvers. I sometimes park wife’s car at some incline. It needs some accelerator pedal I put to release the brake it is holding for hill hold function. I had to “memorize” how it behaves on what it does on what kind of gradient and power (and when, as it also can change because, turbo).
The new breed of torque converters partially used increasing the number of gears as a method to keep the engine closer to efficient ranges, but I have also felt slight hesitations with 8 speed ones. The ratios are so close to each other that where the tf-80sc in wife’s old car would simply go on, they wanted to shift down, or the opposite.
The_Coalition@reddit
A Mercedes 7-speed or 9-speed has basically the same gear spread as the manual 6-speed in a hatchback with added overdrive gears on top. The only benefit of extra gears is a bit of extra efficiency at highway speeds, and even then I found the 9th gear to be relatively unnecessary. But it's great if you have a diesel engine that can run at 1200-1500 RPM while cruising at the speed limit.
dissss0@reddit
They're obsolete in most markets. I believe you can still get them in Indian market Suzuki but that's about it.
The_Coalition@reddit
also in European market Suzukis, and there's also IMTs (manuals with an automated clutch) in Hyundais and Kias here
Kickstart68@reddit
At one time we had a 156 2L and a 156 Selespeed.
I really liked the idea of the Selespeed, but driving it a fair bit I found it disappointing.
While no doubt it could change gear quicker than I could, I was also sitting there waiting for it to finish rather than actually doing something useful.
And in auto mode it scared the hell out of me when it decided it needed to change down 3 gears , so spent what seemed like ages changing down, trying a gear, changing down , trying a gear then changing down again.
While I have access to a modem DCT gearbox car at the moment, and it is quicker at changing gear some of the same issues apply (just not as bad). And even in sport mode the DCT is a lot less "connected" (for want of a better word) - slipping the clutch far more .
It seems to be this abusing the clutch on gear changes that makes modern DCTs smoother to change gear . But honestly it was a non issue for me with the Selespeed (I still tended to back off slightly when changing gear which tended to minimise it on up shifts)
Final-Mammoth2415@reddit (OP)
The "sitting duck moment" most AMT users had -the truck is coming into the intersection, and you are waiting for Selespeed to decide on a gear while watching your life run in front of your eyes! :)
Joke aside, was it a Mk1? I don't know them much, but with mine, changing down one by one would be a serious anomaly. I have an odd one, the 156 JTS never found its way to Turkey, and all 156s including Mk1.5 and Mk2 ones have the 2.0l Twin Spark engine. But I have a JTS Selespeed TCU. I know the one in JTS Selespeeds are different than the Mk1 Twin Sparks, maybe that explains the behavior.
I too have access to a modern DCT, and I agree with you. I feel that it is "overlapping" the clutches, fading even gear clutch out while fading the odd gear in for a 2-3rd shift. I also think part of this comes from the gear ratios being close to each other for the one I have. The rev difference must go somewhere, and that's the clutches as heat.
Kickstart68@reddit
A roundabout with it switching gears aged me significantly!
It was a quite early one (so was the manual). The manual was probably the best saloon I have driven, with the only real issue being needing painful cambelt changes.
Probably quite correct on the close ratios, but also likely overall quite high gearing. I really would prefer it to lock into gear ASAP rather than slipping into gear (it's bad enough on a traditional torque converter auto let alone on a transmission with a clutch where it can be more easily avoided)
Final-Mammoth2415@reddit (OP)
One thing I especially like with the later generation TCU was that it wouldn’t drop from City to manual mode when you manually shift. I have always viewed it a manual car with someone else shifting for you. So coming to a roundabout when I expect sudden acceleration, I shift one down preemptively.
Ah, also, every roundabout is an adventure around here. So you need to be prepared, manual, amt, or auto. I do that with DSG too. People are somehow convinced that the one going straight has the way in roundabouts, not the one in it. :D
Kickstart68@reddit
The DSG we have has a habit of complaining at you if you dare to go into sport of manual mode, saying you could save more fuel in normal Drive. Can be turned off fortunately, but buried in a menu.
yyytobyyy@reddit
Renault multimode hybrid is basically non-synchronized AMT that uses electric motor to rev match. It also has no clutch and no reverse. All those are delegated to the electric motor.
It's not exactly a classic AMT experience, but I think it is the bleeding edge of "modern mainstream AMT".
Final-Mammoth2415@reddit (OP)
Thanks, never looked into it! It seems like it's the traction motor driving the wheels while the engine side (of the transmission) shifts gears, which masks the interruption. Must be some drop in torque tho, at the instant the gearbox is changing gears.
FiatTuner@reddit
ever driven a manual TS 156?
Final-Mammoth2415@reddit (OP)
Yes, a 1.6 TS tho. Plus a couple manual Gt/147s of the same platform.
That might be the reason I am ok. It is much better than torque converters of the era in terms of “spirited” drive, performance and efficiency without me handling the clutch in daily driving. In fact, I don’t think I can do rev-matched shifts better than Selespeed, ever.
Of course other types of auto transmissions have come a long way, but cars have changes as well, in ways I don’t prioritize. And the fact that we have very heavy taxes on cars where I live, which makes really fun cars far less accessible. So Giulia is put of the table for me.
1234iamfer@reddit
ZF Aisin GM Stellantis all developed 8-9-10 gear torque converter based units, who rival the efficiency of AMT/DCT. Also allot of cars are now hybrid, using electric motors to assist and smoothen the gearchange.
Some high end manufacturers tried to add a hydraulic brake of clutch to slow down the input shift, in between shifts to shorten and smoothen the shift time.
Final-Mammoth2415@reddit (OP)
Thanks! I understand that that braking thing didn’t get too much traction (pun not intended :) ) then.
I found that we have one in Turkey as well, Hyundai i10, but I’ve never driven it. Everything else is a dct or torque converter, apart from the few cvts here and there. Wife’s car has a DQ200, and I am questioning the cost and weight tradeoff. Especially being caught off-guard a couple times by the unexpectedly long shifts before I figured out I should be prepared for those when shifting to a gear it didn’t preselect and skip shifting on the same shaft.
UniquePotato@reddit
Most have move back to torque converter as they are smoother, last longer and less conplex