ATF (Automatic Transmission Fluid)
Special fluid for automatic transmissions. Each manufacturer specifies a type (Dexron, Mercon, ZF LifeGuard, etc.). Wrong fluid damages the transmission.
Référence technique
Definitions of technical terms related to automatic transmissions
Special fluid for automatic transmissions. Each manufacturer specifies a type (Dexron, Mercon, ZF LifeGuard, etc.). Wrong fluid damages the transmission.
Manual gearbox with clutch and shifts controlled by an actuator. E.g. Easytronic, SensoDrive. Simpler than a true automatic.
Component that brakes an element of the planetary gearset to obtain a ratio. Wear or incorrect adjustment causes slipping.
A mechanical or hydraulic valve that controls the flow of fluid within the automatic transmission. Faulty check valves can cause gear shifting problems.
A hydraulic component that transmits engine power to the gearbox. It uses fluid to multiply torque and enable decoupling between the engine and the transmission.
Continuously variable transmission with no fixed gear ratios. Uses pulleys and chain or belt. Honda, Nissan, Toyota, Subaru. Specific maintenance.
Dual-clutch transmission. Two shafts, separate clutches for odd/even gears. E.g. DSG, Powershift, DKG. Very fast shifts.
A device that connects or disconnects gearbox elements. Automatic transmissions use multiple clutches to engage different gears.
Engine rotational speed (rpm). TCM uses RPM to optimise shifts and torque converter lock-up.
Ratio change. In automatics, commanded by TCM via solenoids and valve body. Shift quality = indicator of transmission condition.
Ratio between input and output speed. Determines torque and speed of each gear. E.g. 1st = 3.5:1.
Hydraulic control unit housing valves and solenoids. On DSG, called mechatronic module.
Input shaft that receives power from the torque converter and transmits it to the planetary gears. Connects the converter to the gearbox.
Degraded mode activated by the ECU when a fault is detected. Transmission stuck in 3rd or 4th. Protects against further damage.
Main hydraulic pressure generated by the pump. Foundation of operation. Insufficient = slipping and overheating.
Module combining electrical and hydraulic control. Typical of DSG (DQ250, DQ381). Manages solenoids and sensors. Costly part when faulty.
Output shaft that transmits power from the gears to the wheels. Connected to the differential.
Generic code indicating a transmission problem. Secondary codes (P0715, P0720, etc.) specify the cause. Requires OBD-II scan.
Epicyclic gear train. Sun, planets and ring. Combined with clutches and brakes to achieve each ratio.
A component that generates the hydraulic pressure required for automatic transmission operation. A faulty pump can cause pressure loss and transmission problems.
Set of parts for transmission overhaul: seals, clutch packs, filters. Enables complete remanufacture.
Sensor measuring shaft rotation speed (input/output). Fault causes codes P0715, P0720 and often limp mode.
Seal preventing leaks. Turbine seal, shaft seals, etc. Wear = fluid leaks and contamination.
An electro-valve that controls the flow of fluid to the clutches and brakes of the automatic transmission. Faulty solenoids are a common cause of transmission problems.
Fixed part of the torque converter between turbine and pump. Redirects fluid to multiply torque. Internal one-way clutch.
A system using pressurized fluid to actuate clutches, brakes and other automatic transmission components.
Sump or pan containing the fluid. On some units the pan houses the filter. Often fitted with a magnet to capture metal particles.
Rotational force transmitted by the engine. The torque converter multiplies torque at launch. Unit: N⋅m.
Filter that traps contaminants and wear particles. Replace at fluid change. Clogged = pressure loss and overheating.
Special oil providing lubrication, cooling and hydraulic pressure transmission. Manufacturer specification mandatory.
Transmission Control Module/Unit. ECU managing solenoids, sensors and shift strategy. Reads fault codes.
A transmission system that changes gears automatically without driver intervention, using a torque converter and multiple clutches.
The part of the torque converter that receives transmission fluid and transmits power to the gearbox.
A block of valves that controls the distribution of pressurized fluid in the automatic transmission. It is the hydraulic brain of the transmission.
The operation of replacing automatic transmission fluid. Regular fluid changes are essential to keep the transmission in good condition.
Clutch immersed in fluid. Cooled by the fluid. Used in wet-clutch DSG (DQ250, DQ381) and some automatics.
German automatic transmission manufacturer. Common models: 5HP19, 6HP26, 6HP28, 8HP. Used in BMW, Audi, Jaguar, Land Rover, etc.