Q

AUTOMATIC TRANSMISSIONS: What are the different types? 

A

Torque converter automatic

The traditional type employing a torque converter that abosrbs engine power leading to increased fuel consumption and CO2 output.

Can be 2, 3, 4, 5, 6, 7, 8 or 9 ratio, the more ratios the more efficient it will be.

May have manual override for which different manufaxcturers have different brand names, for example 'Tiptronic', 'Geartronic', 'Autotronic'.

The manual shifter may be a nudge forwards/backwards shifter on the quadrant, may 'slap' side to side (on Mercedes and Chryslers) or may have steering wheel button or paddle shifters.

Mazda 6-speed Skyactiv compact torque converter automatic transmission have proved to be very good.

Continuously Variable automatic

(Shortenend to CVT and brand-named 'Multitronic' by Audi. )

This employs conical pulleys and steel belts to 'continuously' change ratios, now generally optimised at 7, which can be selected and held by the driver to a point if he or she wishes.

Alternatively it may work as an epicyclic CVT, as fitted to Toyota hybrids such as the Prius.

Audi, Nissan, Honda (in the Jazz) and Mercedes (in the A and B Class) offer CVTs. In the Primera, Nissan combined a CVT transmission with a torque converter rather than an electromagnetic clutch to take up initial drive.

CVTs are generally much more fuel efficient than Torque Converter autos.

The CVT fitted to Nissan Primeras proved to be very reliable. One reader never changed the fluid in 99,000 miles because it remained clean as new. Comments from North American users on the internet agree with this. However, the CVTs fitted to first generation Nissan Qashqais and Jukes proved to be anything but reliable with a very high failure rate resulting in a lot of warranty and post warranty claims.

Nissan CVTs don't appear to be able to hold 2nd gear on slippy surfaces when setting off (equivalent of the Snow button on some old Autos). A real pain on icy / snowy roads or even slight uphill wet grassy fields.


Direct Shift Gearboxes

For example VAG's transvverse engine twin-shaft 6-speed manual transmission with a pair of oil clutches. Because the next ratio is always on the opposite shaft, it can be 'pre-selected' and changed to rapidly and efficiently, usually at no sacrifice in fuel economy. They work either fully automatically or with driver control by nudge shift or paddle. Audi has re-named DSG 'S-Tronic'. VAG now offers a twin dry clutch DSG/S-Tronic with its smaller engines and a new twin wet clutch 7-speed DSG/S-Tronic for diesel engines with up to 500Nm torque.

Ford (Getrag), Mitsubishi, Renault, Alfa Romeo, Hyundai and KIA now also offer twin shaft, twin clutch transmissions.

These are the different Volkswagen DSG and S tronics: 

DQ200 is a seven speed transverse DSG with a dry clutch pack used in all five brands. The gearbox code in the diagnostic log shows 0AM and or 0CW. This gearbox does not have a service requirement as it is sealed for life. Fittted to 1.0 litre to 1.8 litre petrol and diesel engines.

DQ400 is a six speed transverse DSG with a wet clutch pack and is used in the Golf Hybrid and Passat GTE and also Audi A3 etron the gearbox code in the diagnostic log shows 0DD. The gearbox also has a service requirement of 40,000 miles

DQ250 is a six speed transverse DSG with a wet clutch pack. The gearbox code in the diagnostic log shows 02E and or 0D9. This also has a service requirement of 40,000 miles. Fitted to 2.0 litre petrol and diesel engines.

DQ381 is a seven speed transverse DSG with a wet clutch pack and torque capacity of 420-430Nm.

DQ500 is a seven speed transverse DSG with a wet clutch pack and a torque capacity of 600Nm, mainly used in the Tiguan and Audi Q3 it can also be found in the CV T5, the gearbox code in the diagnostic log shows 0BH and or 0BT. This also has a service requirement of 40,000 miles. Fitted to 2.0 litre 4-cylinder petrol and diesel engines and 2.5 litre 5-cylinder petrol engines.

DQ511 is a ten speed transverse DSG with a wet clutch pack and a torque capacity of 550Nm.

DL382 is a seven speed longitudinal DSG with a wet clutch pack and a torque capacity of 400Nm, used in front wheel drive Audi A4, A5 and A6.

DL501 is a seven speed longitudinal DSG with a wet clutch pack and a torque capacity of 600Nm, used in Quattro four wheel drive Audi A5, A6, A7 and A8, and the Porsche Macan.


Automated Clutch Manuals

These are really manual boxes with electronically controlled electric motorised clutches controlling the gearshifts either 'fully automatically' or by the driver using a shift lever or paddles. Employed in cars from Ferraris to Citroen C1s. Variously called M/M. MMT, F1, R-Tronic, Sensodrive, EGS, Easytronic, Durashift. Can be very difficult to achieve a smooth change from 1st to 2nd with these boxes. But they are getting better. The EGS in the new Citroen C4 and C4 Picasso is quite good. Can also bring benefits in fuel economy and C02 output,. The Citroen C4 1.6 HDI 110 EGS emits less than 120g/km CO2.  

 

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