Truck transmissions

For trucks needing more gears, the standard "H" pattern can get very complicated, so additional controls are used to pick additional gears. The "H" pattern is retained, then an additional control selects among options. In older trucks, the control is often a separate lever mounted on the floor or more recently a pneumatic switch mounted on the "H" lever; in newer trucks the control is often an electrical switch mounted on the "H" lever. Multi-control transmissions are built in much higher power ratings, but seldom use synchromesh.

Some trucks have transmissions that look & behave like ordinary automobile transmissions - these transmissions are used on lighter trucks, usually have up to 6 gears, & usually have synchromesh.

There's several common options for the shifting pattern. Usual types are:

• Range transmissions use an "H" pattern through a narrow range of gears, then a "range" control shifts the "H" pattern between high & low ranges. For example, an 8-speed range transmission has an H shift pattern with gears. The first through fourth gears are accessed when low range is selected. To access the fifth through eighth gears, the range selector is moved to high range, & the gear lever again shifted through the first through fourth gear positions. In high range, the first gear position becomes fifth, the second gear position becomes sixth, & so on.
• Splitter transmissions use an "H" pattern with a variety of gears, & the other selector splits each sequential gear position in: First gear is in first position/low split, second gear is in first position/high split, third gear is in second position/low split, fourth gear is in second position/high split, & so on.
• Range-Splitter transmissions merge range-splitting & gear-splitting. This allows even more gear ratios. Both a range selector & a splitter selector are provided.