ZF AS Tronic is a semi-automatic/manual transmission made by ZF Friedrichshafen for the motorcoach and lorry market in Europe and North America which was first introduced in 2003. To the driver, it behaves like an automatic transmission, but allows the driver to switch from a manual mode with a touch of a button. Note though, it takes longer to reach full speed on a bus with this transmission than it does with a bus equipped with, say, an Allison B500R automatic transmission.
As it is in part a manual transmission, it lacks the torque converter that is standard on automatic transmissions-an AS Tronic has been quoted as being 500 pounds less than the B500. Some coach operators are choosing this transmission for better fuel economy over automatics.
This transmission is offered as a 6-speed(called AS Tronic Lite by ZF), 10-speed 12-speed or 16-speed transmission.