Different Types of Automatic Transmission

Honest John Back Room » Technical matters
View Threaded
Tue 25 Aug 2020 21:26
Different Types of Automatic Transmission - Chubba

Hello

What's the difference between the various automatic transmission types? From reading on here, I've seen references to torque converter, automated manual, CVT and semi-automatic. Are there any other types? Is one type better than the other?

I have a Hyundai i30 1.6 CRDI Auto 13 reg. I've always thought it was a semi-automatic as I can switch to manual shifting but is that a correct assumption?

Thanks

Reply | Report as offensive | Link
Tue 25 Aug 2020 21:40
Different Types of Automatic Transmission - RT

Almost all modern automatics have manual shifting as one of their modes so that's not definitive

Reply | Report as offensive | Link
Tue 25 Aug 2020 22:00
Different Types of Automatic Transmission - daveyjp

Even older autos had lock up which is a form of manual changing,

Reply | Report as offensive | Link
Tue 25 Aug 2020 22:22
Different Types of Automatic Transmission - mcb100
Most prevalent today is the DCT, or dual clutch transmission, used by many manufacturers and known by many names (DSG being the best known). As the name suggests, there are two clutches, one on the odd numbered gears and one on the even.
From standstill, 1st gear is selected and it’s clutch engaged. As the drive accelerates, the control unit predicts that 2nd will be needed next, so selects it but doesn’t yet engage the clutch. At the appropriate point, the clutch on first gear disengages and the clutch on 2nd engaged, the time taken being measured in milliseconds. Third is now selected, and it’s clutch readied for engagement as the clutch on second disengages. And so on.
Whilst decelerating, the gearbox will ready the next lower gear in anticipation.
Because, in effect, it’s an automated version of a manual gearbox, fuel economy should be close to that of the equivalent manual.
Either leave it in automatic mode or control it via the gear selector lever or paddles (if fitted), the choice is yours.

Edited by mcb100 on 25/08/2020 at 22:23

Reply | Report as offensive | Link
Wed 26 Aug 2020 06:54
Different Types of Automatic Transmission - edlithgow

My understanding is/was that a semi-automatic transmission was a manual gearbox with an "automatic" clutch, Fairly rare on cars but a feature of the worlds most numerous vehicle, the Honda C90 and its derivatives, which has a centrifugal clutch.

I think the Mk1 Renault Twingo (which I quite fancy, they used to assemble them in Taiwan but few survive) was, or could be, a semi-automatic.

I vaguely remember that some autoclutches were electromagnetic but dunno model specifics

Edited by edlithgow on 26/08/2020 at 06:55

Reply | Report as offensive | Link
Wed 26 Aug 2020 12:39
Different Types of Automatic Transmission - galileo

My understanding is/was that a semi-automatic transmission was a manual gearbox with an "automatic" clutch, Fairly rare on cars but a feature of the worlds most numerous vehicle, the Honda C90 and its derivatives, which has a centrifugal clutch.

I think the Mk1 Renault Twingo (which I quite fancy, they used to assemble them in Taiwan but few survive) was, or could be, a semi-automatic.

I vaguely remember that some autoclutches were electromagnetic but dunno model specifics

I think Rootes used a magnetic clutch on Hillman Minx cars way back when I was a lad. Standard offered a two-pedal system around the same time but using a centrifugal clutch.

Reply | Report as offensive | Link
Wed 26 Aug 2020 14:57
Different Types of Automatic Transmission - bathtub tom

the Honda C90 and its derivatives, which has a centrifugal clutch.

IIRC the Honda 'step throughs' only used the centrifugal clutch for pulling away. A cam on the gearchange operated the clutch for gear changes (never seemed to be adjusted).

Reply | Report as offensive | Link