How Many Gears Are In a Semi Truck?
Semi trucks, also referred to as tractor trailers, are the long haul transport vehicles for goods and materials on highways across North America. Semi trucks have many parts that work together to lift, pull, and maneuver trailers, and they come in a variety of truck types that use different engine and transmission systems.
Types of Gear Control
Semi trucks are equipped with conventional manual transmissions or automated manual transmissions (AMTs) depending on the make and model. Generally, manual transmission semi trucks are equipped with either 10-speed or 13-speed gear boxes. Semi trucks with AMTs can have up to 18 gear speeds.
Manual transmissions use a clutch system and gear shift to control the speed and power that the engine puts into the wheels. When a driver changes gear, they release the clutch while simultaneously pressing down on the gas pedal to increase RPMs and shift up into the next gear.
- 10-Speed Transmissions – 10-speed semi trucks have 10 available gear ratios that allow for increased acceleration and torque. The most common 10-speed transmission uses 4 main gears in a double H pattern shift, and it is also the lightest manual transmission with fewer components than 13-speed transmissions.
- 13-Speed Transmissions – 13-speed transmissions are the most popular type of manual transmission in semi trucks. This transmission has a double H pattern shift and 6 additional gears spliced between the main ones, allowing for a more precise gear selection and a wider range of gear ratios.
Automated Manual Transmissions (AMTs)
Automated manual transmissions (AMTs) use an electronic control system to automatically shift the gears in a semi truck. Through the use of sensors and computers, an AMT transmission can identify the best gear ratios for type of terrain and load while also optimizing fuel efficiency.
AMT semi trucks are becoming increasingly popular, as they reduce the stress on drivers by eliminating the need for them to manually shift gears. The number of gear ratios depends on the make and model, but AMT semi trucks typically have between 8 – 18 speed gear ratios.
Semi trucks come equipped with either manual transmissions with 10-speed or 13-speed gear boxes, or automated manual transmissions with up to 18 gear speeds. Manual transmission semi trucks require a driver to physically shift the gears, while automated manual transmission semi trucks use sensors and computers to select the best gear ratios for fuel efficiency and road conditions.