Fleet and transmission glossary.
Plain-English definitions of terms used in our fleet and transmission guides.
Valve body
The valve body is the hydraulic control assembly inside an automatic transmission. It is a maze of passages and valves that directs pressurized transmission fluid to apply the clutches and bands at the right time. Its valves and passages control when and how firmly the transmission changes gears.
Torque converter
The torque converter is the fluid coupling between the engine and an automatic transmission. It lets the engine keep turning while the vehicle is stopped and multiplies torque when the vehicle launches. Many torque converters also include a lock-up clutch that mechanically links the engine to the transmission at steady speeds, removing the fluid slip.
CSA score
CSA stands for Compliance, Safety, Accountability, a program run by the Federal Motor Carrier Safety Administration (FMCSA). Its Safety Measurement System gives a motor carrier a percentile score in each of several BASIC categories, such as unsafe driving and vehicle maintenance. The scores are calculated from roadside inspection violations, crash data, and investigation results, and ranked against similar carriers.
DOT Level I inspection
A Level I inspection is the most thorough of the North American Standard roadside inspection levels. It combines a check of the driver's credentials and records with a detailed inspection of the vehicle, including items checked from under the vehicle. It is performed by certified inspectors.
Severe-duty interval
A severe-duty interval is a shorter maintenance interval for vehicles operated under severe-service conditions. Examples include towing, carrying heavy loads, frequent stop-and-go driving, and dusty or extreme-temperature environments. It is used in place of the normal interval, which assumes easier operating conditions.
6R80
The 6R80 is a six-speed automatic transmission made by Ford. It is used in many Ford trucks and SUVs, including the F-150. It is a longitudinal transmission used in rear-wheel-drive and four-wheel-drive vehicles.
Synchro
Synchro is short for synchronizer, an assembly in a manual transmission made up of a ring and a sleeve. It matches the speed of a gear to the shaft it is about to lock onto. This lets the gear engage smoothly without grinding.
PM interval
A PM interval is the planned amount of mileage or time between preventive maintenance services. Those services typically include fluid changes and inspections. The interval is usually set by the vehicle manufacturer, the operator, or both, and may be shortened for severe-duty use.