• Trucks come in a variety of shapes and sizes.truck image by Tomasz Pawlowski from Fotolia.com
  
  Trucks are vehicles used for carrying a variety of cargo. They have engines suited to the weight of the cargo and the distance it needs to be transported, a body shaped to carry the cargo and easily enable its loading and removal, and a cab in which the driver and any passengers can sit.
  
  

Body

• Tipper trucks make use of a hydraulic arm to lift the open-topped body at one end. Goods are released through the tailgate. Box-bodied trucks have a rigid body with solid sides. Entry is through the rear end via doors or rolling shutters. Curtain-sided trucks have a solid frame in the shape of a box, their soft-curtained sides mean that goods can be more-easily loaded and unloaded. Flat-bed trucks carry goods on the platform body at the rear. Trucks required to carry goods needing refrigeration or freezing will have bodies that can be temperature-controlled. Trucks with an additional section that stretches over the cab are known as Luton peak bodies. The bodies of road tankers consist of a permanently fitted tank used in the safe transportation of gases, powders and liquids.
  
  

Transmission

• The transmission consists of a complex set of gears that transfers the engine's torque through to the drive-wheels. Small trucks use either an automatic or a manual transmission with synchronizers to ensure that the teeth of the gears mesh together. Larger trucks may use manual transmissions without synchronizers. These require the driver to either change gears with the use of the clutch or make use of a method whereby the gears are synchronized by revving the engine before engaging the gear. In the U.S., large trucks commonly have between nine and 15 gears. In the U.K., those with manual transmission have between eight and 12 gears.
  
  

Cab

• Cabs are where the driver and passengers sit. In small trucks, these are either standard day cabs or crew cabs. Crew cabs can accommodate more people but will reduce the available space for loading goods. Some cabs feature a sleeping compartment so that the driver can rest during long journeys. Cabs are most commonly built either over the engine or behind it. Cab-over-engine designs reduce the overall length of a truck so they are more useful in areas where turning space is restricted. Some specialist trucks -- such as those found in airports or shipping yards --- are designed with the cab built beside the engine.
  
  

Engine

• A truck should have an engine that matches its intended use. Ideally, they should run so that maximum torque is achieved at the most-commonly used engine speed. As a general rule, engines intended for use over long distances or at high speeds will be more powerful. While some smaller trucks may be petrol-powered, virtually all larger trucks run from diesel. Hybrid-electric engines are becoming more common as fuel prices increase and due to environmental concerns.