Truck Equipment Glossary - U

Underlift
A device used for towing vehicles by lifting one end of the towed vehicle from under the axle or structural member.
 
Universal Joint
Truck drive shafts have universal joints to allow for vertical motion of drive axle and change of angle due to truck loading. Universal joints are used wherever a drive or control shaft must have a change of angle along its axis.
 
Unloaded Vehicle Weight
The weight of a vehicle with maximum capacity of all fluids necessary for operation of the vehicle, but without cargo, occupants or accessories that are ordinarily removed from the vehicle when they are not in use.
 
Unsprung Weight
All the vehicle weight that is not supported by the truck’s springs, including wheels, tires, brakes, axles and drive shaft. The objective of design engineers is to reduce unsprung weight to a practical minimum.