Gone are the days when the non-synchro’ gearbox was king. Many large lorries come with an automated manual transmission (AMT) such as the Eaton AutoShift, Renault Optidriver, UD Trucks ESCOT, Volvo I-Shift or Mercedes-Benz PowerShift. Automated manual transmission is not the same as automatic transmission – there’s no torque converter. They are a modified manual gearbox where electronics control the gearshift rather than the driver.
Unlike a driver whose clutch leg might get tired in slow-moving traffic, an automated manual will produce perfect shifts time after time at the optimal rev range for the conditions. This improves fuel economy, reduces wear and tear on the vehicle, reduces noise outside the vehicle, reduces driver fatigue and improves driver satisfaction. As margins for transport companies are thin, any savings in fuel economy are welcome, and drivers find them easier to use, particularly as they don’t need to learn how to use a non-synchro ‘box like a Roadranger. You can learn how to use a Roadranger gearbox here.
How does an AMT work?
Computer controlled actuators (air cylinders, electric motors or both) move selector rods and range/split selectors in combination with clutch application to do the gear change. The driver doesn’t have to do any of that with a clutch and gearstick. The computer monitors the engine load in relation to the revs and the road speed and decided whether or not a different gear would be better. It perfectly matches the clutch and revs to make a rapid but smooth gearshift.
The driver can override the AMT – this is useful if, for example, the driver wants to keep the lorry in a low gear – but technology now is much better than humans at choosing the best gear for fuel economy and comfortable driving, so in most cases it’s best to let the computer to its thing.
Older AMT systems still required the driver to use the clutch and gears to get the truck moving, then would take over at higher speeds, but modern AMT systems driver like an automatic car drives.
Are there any problems with automated manual transmissions?
If you leave the lorry in gear and there’s an air leak, you won’t be able to get it started and it will be impossible to take it out of gear because the gearshifts are air-operated. It would need a mechanic to come out and manually fill the air tanks.