Truck Equipment Glossary - P

Parallel Batteries
All batteries have their positive terminals connected on a separate wire and all negative terminals on another separate wire. This means that four six-volt batteries (some trucks carry four batteries) will still produce only six volts, but will have four times the energy potential.
 
Payload
The weight of the commodity being hauled. Payload capacity is computed by subtracting the completed weight of the vehicle (including driver and passengers) from the GVWR.
 
Payload & Body Allowance
The payload capacity of the truck with allowance for the weight of a truck body.
 
Peddle Truck or Shuttle Truck
Terms for the city delivery trucks owned by a long-distance hauler. They distinguish between the big “rigs” and the small city trucks.
 
Percent of Grade
The figure used in computing the power requirements of a truck. Usually taken at the steepest grade a truck will be required to climb on its route. Percent of grade is determined by dividing the height of a hill by its length.
 
Pintle Hook
Hook mounted on a truck or semi-trailer used to couple a full trailer.  
 
Pitch Line Velocity (PLV)
The circumference in feet at the pitch line of a gear multiplied by the RPM of that gear at 1,000 engine RPM. A small PTO driving gear in the transmission gives a low pitch line velocity; a larger gear gives a correspondingly higher pitch line velocity.
 
Platform/Flatbed
Load-carrying bed with or without removable sides. May be equipped with hydraulic cylinders to tilt and slide platform.  
 
Ply Rating
A standard unit of tire casing strength, based on the strength of cotton plies. This term is used to indicate the load-carrying ability of a given tire. It is an index of tire strength and does not necessarily represent the number of cord plies in the tire.
 
Pole Trailer
A motor vehicle without motive power designed to be drawn by another motor vehicle and attached to the towing vehicle by means of a reach or pole, or by being boomed or otherwise secured to the towing vehicle. Used for transporting long or irregularly shaped loads such as poles, pipes or structural members generally capable of sustaining themselves as beams between the supporting connections. 
 
Power Curve
A graphic illustration of maximum output of horsepower and torque at all operating speeds. These curves are established from data obtained by running a sample engine on an engine dynamometer. Curves are established using bare operable engine and with standard accessories. Net power figures (those using standard accessories) are used in vehicle performance calculations. 
 
Power Divider
Usually a small auxiliary gear box or chain-driven device to allow distribution of drive shaft power to several different mechanical devices mounted on the same truck.
 
Power Take-off (PTO)
A mechanical device used to transmit engine power to auxiliary equipment. Power take-offs can be mounted on either a main or auxiliary transmission. Front-mounted and flywheel-mounted power take-offs are also used in various applications.
 
Power Train
All the components that handle the engine power from the truck engine to the driving wheels. This includes transmissions, drive shafts, as well as differentials and driving axles. 
 
Private Fleet
A truck fleet owned for a company’s own use.  
 
Push Bumper
Device used to push a vehicle, sometimes equipped with a rubber face. 
 
Pusher Axle
An auxiliary axle installed in conjunction with the rear axle(s) of a truck chassis. A pusher axle is installed ahead of the drive axles, thus shortening the length of the wheelbase.