Sure glad he didn't ask about the Hydrostatic transmission - I would refer him to his local Linde man.

Lift truck transmissions course 101

Manual transmission - is a mechanical transmission using gears as primary method to transfer power from teh engine to the driving axle. It requires a clutch disc & pressure plate and is operated usually by the left foot with pedal in the operators compartment. When teh pedal is depressed the operator can select forward or reverse travel & various speed ranges.

Power Shift transmission - a transmission that utilizes a torgue converter & hydraulically applied clutches that allows the transmission to change directions with a lever that activates a hydraulic valve on the transimission. Typically, most Power Shift transmission are single speed.

Automatic transmissions - are similar to Power shift transmissions except they can have 2, 3 or 4 different speed ranges. A true automatic transmission will shift from low range to the high ranges "automatically" similar to an automobile. In lift truck operations sometimes a lock out of the automatic shifting is provided when high driving power is required for an extended period - like getting stuck or carrying a heavy valuable load, etc.