Not all automatic gearboxes are equal

Posted on December 16th, 2013 by Rob Marshall

RM-blog1-Dec13More and more GEM members are seeking advice on the latest generation of automatic transmissions, whether it is purchasing guidance, or help, after an expensive mechanical breakdown. Confusion, it seems, is rife.

Recently, carmakers have made successful progress in developing a new range of automatic gearboxes that sap neither fuel nor power. In truth, these are really automated manuals, in that they are manual gearboxes, with their clutches and gears operated robotically.

Unfortunately, few companies have chosen to inform their customers of the difference. The centre console might be still marked with the traditional ‘P’, ‘R’, ‘N’ and ‘D’ labels but the automated manual is very different to the heavier, planetary geared automatic transmission. To confuse things further, traditional features of older transmissions have been engineered into automated manuals, such as the ‘creep’ function.

Yet, because they work differently, the new transmissions still require a different driving method, to ensure smooth progress. Considered throttle inputs help to not only facilitate a more gradual take-off and smooth gear changes but will also enhance mechanical life. After speaking to a few transmission re-builders, several problems can be attributed to drivers, who might be unaware that automated manual gearboxes are under greater mechanical stress and abrupt and erratic throttle movements can affect reliability.

It seems that car salesmen might be confused as well. On reading a motor dealership trade magazine earlier this year, a columnist claimed that the manual gearbox had been rendered obsolete, thanks to the new generation of ‘automatics’. Clearly, the writer did not know the difference between an automatic and an automated manual, so how could we expect the same of his retail motor trade audience? The increase in GEM members enquiring about the subject leads me to conclude that salesmen need to spend more time learning about these transmissions and advising their customers accordingly, before encouraging them to sign the order forms.

Prior to making any decisions, take the car for an extended test-drive and do your research carefully, before buying. Generally speaking, there are several ‘automatic’ options available on the new and nearly-new car scenes.

1.  Conventional planetary geared automatics – These units continue in production and are modernised versions of the older hydraulically-operated types. Most have torque converter clutches, although not all of them do, such as ZF’s 8HP unit. These types tend to be fitted to higher powered cars. Such examples are Audi’s Tiptronic and Mercedes-Benz’s 7G-Tronic.

2.  Automated Manuals. These are either:

a.  Single clutch – This is the purest type of automated, or robotised manual gearbox, because that is exactly what it is. The manual clutch pedal and gear lever are replaced simply by electronic and hydraulic controls, activated by a computer. Examples are Volkswagen’s ASG, Peugeot’s EGS and Fiat’s Dualogic

b.  Twin Clutch – This unit consists of a pair of manual transmissions, within one casing. Gear changes are made by internal clutch plates and, when activated, can effect a gearshift within milliseconds. Examples include VW’s DSG and Renault’s EDC.

3.  CVT (Continuously Variable Transmission) – This does not rely entirely on gears, as a belt is used instead to give infinite ratios. Carmakers tend to set ‘step’ points within the electronics, to make the transmission feel more closely akin to a conventional automatic. Examples are Subaru’s Lineartronic and Audi’s Multitronic.