The oddities of automatic gearboxes

The oddities of automatic gearboxes

Author
Discussion

BucksFizz

Original Poster:

203 posts

173 months

Wednesday 2nd September 2015
quotequote all
Although automatics are not my preference I can understand why they are popular, but what I find peculiar is the huge difference between old style torque converts and the latest double clutch offerings.

For example let’s say on a typical journey I change gear 50 times in a manual, a torque converter box also changes gear 50 times, but a double clutch will change 150.

Although I’ve driven a few different variants of each box I going to call out PDK as being the worst offender here, up down up down up down for fk sake pick a gear! It always feels like the gearbox is in a rush, maybe this is not helped with 7 gears?

By comparison something sporty but with a traditional auto box is just such a more pleasant and less frustrating experience, and you can put them in sport mode without the artificial transmission shunt you get with PDK.

Just wondering if anyone has noticed this?

kambites

67,462 posts

220 months

Wednesday 2nd September 2015
quotequote all
Are you sure it's not just down to the PDK having more gears?

anonymous-user

53 months

Wednesday 2nd September 2015
quotequote all
I miss the 3 gears and overdrive. I cant wait until we have cars with 1 gear does all.

Howard-

4,950 posts

201 months

Wednesday 2nd September 2015
quotequote all
If anything, my dual-clutch auto seems less inclined to constantly change gears than many torque converter autos I've driven. I think it depends on the engine and its spread of torque, and how the gearbox has been programmed to work with this.

LordGrover

33,532 posts

211 months

Wednesday 2nd September 2015
quotequote all
... a bit like DAF did?

Superhoop

4,676 posts

192 months

Wednesday 2nd September 2015
quotequote all
The Spruce goose said:
I miss the 3 gears and overdrive. I cant wait until we have cars with 1 gear does all.
We do, they're called CVT

anonymous-user

53 months

Wednesday 2nd September 2015
quotequote all
Superhoop said:
We do, they're called CVT
No eletric motors in wheels, CVt aren't single gears.

sjg

7,444 posts

264 months

Wednesday 2nd September 2015
quotequote all
Emissions testing plus more ratios available means all modern autos are very keen to change up as soon as they can in whichever "normal" mode.

ZF 8-speed is almost CVT-like if you're accelerating gently, it can make it through 5 gears without the revs changing much at all.

Otispunkmeyer

12,557 posts

154 months

Wednesday 2nd September 2015
quotequote all
Howard- said:
If anything, my dual-clutch auto seems less inclined to constantly change gears than many torque converter autos I've driven. I think it depends on the engine and its spread of torque, and how the gearbox has been programmed to work with this.
I like a good Torque converter auto because of the smoothness, but the one on my Volvo is a bit harsh when cold, hanging on to a gear then jolting into the next one (I suspect the ATF needs replacing). Its also the only autobox I have had that likes to kick down a gear at the slightest depress of the go pedal. Quite annoying when, if you can make it stay in gear, the engine is quite capable of getting the car to accelerate smoothly.

300bhp/ton

41,030 posts

189 months

Wednesday 2nd September 2015
quotequote all
kambites said:
Are you sure it's not just down to the PDK having more gears?
I've not been in or driven a PDK car. But I can say my Roadster is awful in auto mode, it seems to be on a constant mission to keep the revs as high as possible. And won't settle in a single gear very well.

I suspect/wonder if other automated manuals (of any type) suffer this too.

Although I'd have thought a lot of it is down to programming.

That said a torque converter by it's very nature allows more flexibility as often it's just a case of unlocking the converter rather than actually needing a gear change.

Hungrymc

6,643 posts

136 months

Wednesday 2nd September 2015
quotequote all
it amazes me how quickly dual clutch boxes go through the first few gears. out of 1st as soon as the car is rolling. I like them when moving but do find their behaviour in stop start conditions a little irritating.

romeogolf

2,056 posts

118 months

Wednesday 2nd September 2015
quotequote all
7G-Tronic in my SLK was almost flawless in giving a smooth drive. Sometimes got confused if you went from strong acceleration to harsh braking (ie: See a roundabout gap, foot down to go, then realise car on the roundabout has changed mind and isn't exiting) and the car would feel like it's "jumping".

On the other hand the 6-speed auto in the Mini Paceman I'm using at the moment seems to struggle to find the right gear, always shifting down at the smallest of throttle inputs. Really poor experience.

Mr E

21,583 posts

258 months

Wednesday 2nd September 2015
quotequote all
Hungrymc said:
it amazes me how quickly dual clutch boxes go through the first few gears. out of 1st as soon as the car is rolling. I like them when moving but do find their behaviour in stop start conditions a little irritating.
Surprised it doesn't pull away in second to be honest. Our merc only uses first if you've pushed the sport button or pulled a paddle and asked for it.
I imagine it may kick down to first if heavily loaded and on a serious hill, but I've not tried.

FredClogs

14,041 posts

160 months

Wednesday 2nd September 2015
quotequote all
Surely modern autos with 6 or 7 gears are just trying to keep you with the regulated Carbon output zone and improve your MPG...?

dubloon

64 posts

104 months

Wednesday 2nd September 2015
quotequote all
I prefer a good modern torque converter transmission to the twin-clutch autos. Much more satisfactory in tedious stop start driving.

rallycross

12,747 posts

236 months

Wednesday 2nd September 2015
quotequote all
I've had a few auto's recently that only have 4 gears including swift 1.5 auto, Hyundai coupe auto, the surprising thing was they drove fine for what they were, and now we are mostly used to at least 6 gears let alone 4.

300bhp/ton

41,030 posts

189 months

Wednesday 2nd September 2015
quotequote all
rallycross said:
I've had a few auto's recently that only have 4 gears including swift 1.5 auto, Hyundai coupe auto, the surprising thing was they drove fine for what they were, and now we are mostly used to at least 6 gears let alone 4.
I guess that depends how much exposure you have the new and higher end cars though. The market might be filled with such vehicles, but not everyone drives a new car.

hoppo4.2

1,531 posts

185 months

Wednesday 2nd September 2015
quotequote all
Old auto boxes change gear based on internal speeds/ fluid pressures etc.

Modern auto boxes with torque converters are electronically controlled and change based on all sorts of factors. My old man's saab 2.8 aero was terible could never make up its mind.

The same is true for all these pdk type systems it's all down to how the brain is programed