Drivetrain part descriptions
G - Z
Gear Position Sensor
The gear position sensor, located on the automatic transmission, communicates the gearshift’s position to the vehicle’s electrical system. It enables starting the car in Park/Neutral, engaging Drive/Reverse, and turning on backup lights. A bad sensor can prevent starting, cause incorrect gear shifts, trigger limp mode, or illuminate the check engine light.
Gearbox Oil
Gearbox oil lubricates and cools transmission components, preventing wear and ensuring smooth gear shifting. It should be changed periodically according to the vehicle manufacturer’s recommendations to maintain optimal performance and extend the life of the transmission.
Manual Transmission Fluid
Manual transmission fluid lubricates and cools the transmission. It’s usually gear oil, but some use engine oil or automatic transmission fluid. Over time, it breaks down and gets contaminated, leading to transmission damage. Replace at the manufacturer’s recommended interval or during significant transmission repairs to prevent issues.
PCM (Powertrain Control Module)
The PCM (Powertrain Control Module) is a powerful computer that manages the engine, transmission, and other powertrain components. It monitors ignition, fuel injection, emissions, and more. The PCM alerts drivers of issues through warning lights and stores diagnostic trouble codes for technicians to retrieve and diagnose.
Shift Solenoid
A shift solenoid is a component in an automatic transmission that controls the flow of hydraulic fluid to engage gears. It consists of a plunger surrounded by a magnetic coil. When activated by the transmission control module, the solenoid allows fluid to flow, enabling the transmission to shift gears.
Torque Converter
The torque converter is located between the engine and transmission. It consists of an impeller, turbine, stator, and sometimes a converter clutch. A faulty torque converter can cause various issues like poor acceleration, overheating, slipping, and strange noises. Replacing a bad converter can be expensive.
Transaxle
A transaxle is a single mechanical unit that combines a transmission and differential to transmit power from the engine to the wheels. It is commonly used in front-wheel drive, rear-engine, mid-engine, and some front-engine rear-wheel drive vehicles for improved packaging and weight distribution.
Transfer Case
A transfer case distributes power from the engine to the front and rear wheels in 4WD and AWD vehicles, providing better traction in various driving conditions. Signs of a bad transfer case include strange noises, difficulty shifting gears, unexpected 4WD engagement/disengagement, fluid leaks, burning smells, and warning lights.
Transmission
The transmission transmits power from the engine to the wheels, using gears for different speeds. Problems include warning lights, noises, rough shifting, leaks, and the vehicle not moving. Transmission issues are often expensive to fix, so early diagnosis is important to potentially save money on repairs.
Transmission Cooler
A transmission cooler is a small radiator that cools automatic transmission fluid circulating through the transmission. It can be a separate unit or integrated into the engine radiator. The cooler allows the transmission to work more efficiently by pumping hot fluid through metal lines to be cooled and returned.
Transmission Pan Gasket
The transmission pan gasket is a mechanical seal located between the transmission and its oil pan. It prevents transmission fluid leaks. Symptoms of a failing gasket include fluid leaks and the Check Engine Light turning on. The gasket should be inspected and replaced if necessary when the pan is removed.
Transmission Pump
The transmission pump, driven by the torque converter, creates fluid flow and pressure in automatic transmissions. A failing pump can cause whining noises, transmission slippage, check engine light activation, no movement in any gear, and fluid leaks. Repairs usually require removing the entire transmission and torque converter.
Transmission Rear Oil Seal
The transmission rear oil seal is a mechanical seal located between the transmission and driveshaft that prevents fluid leaks. Symptoms of a failing seal include transmission fluid leakage. When replacing the seal, inspect the driveshaft sealing surface for damage and check the rear transmission mount for oil soaking.
Universal Joint
A universal joint (U-joint) is a component in rear-wheel, four-wheel, and all-wheel-drive vehicles. It connects the transmission to the differential or transfer case, allowing for up-and-down movement of the driveshaft or axle. Worn U-joints can cause clunking noises, vibrations, and even render the vehicle inoperable.