ASE PS2 Test Preparation Guide: Automatic Transmission/TransaxleAutomatic

Automatic Transmission TransaxleThere are two types of automatic transmissions and transaxles: mechanical and electronic.  Mechanical automatics use engine speed, throttle cables, governors and valves to shift gears, while electronic automatics use engine rpm and sensor inputs to operate solenoids that route internal fluid pressure to shift gears. Inputs include throttle position, engine load (vacuum), vehicle speed and other sensor data that are fed to the transmission control module (TCM) and/or powertrain control module (PCM). The transmission module may be located on the transmission, elsewhere in the engine compartment or combined with the PCM, and may also communicate with the ABS/traction control system and modify its operation as needed.

Most automatic transmissions are coupled to the engine with a torque converter, a fluid coupling mounted on the flywheel that transfers and multiplies engine torque to the transmission like a set of reduction gears. Inside the torque converter is a three-piece set of closely spaced blades (the “turbine, stator and impeller”). As the torque converter rotates, fluid is thrown from one set of blades against the other, pushing the blades connected to the transmission input shaft and planetary gears to drive the vehicle down the road. Most torque converters have a “lockup clutch” that engages hydraulically when controlled by an electronic solenoid valve to physically couples the engine and transmission in higher gears to eliminate slippage for improved fuel economy. On some of the latest automatics, an electromechanical clutch is used to couple the transmission to the engine. The torque converter holds approximately

Most automatic transmissions are coupled to the engine with a torque converter, a fluid coupling mounted on the flywheel that transfers and multiplies engine torque to the transmission like a set of reduction gears. Inside the torque converter is a three-piece set of closely spaced blades (the “turbine, stator and impeller”). As the torque converter rotates, fluid is thrown from one set of blades against the other, pushing the blades connected to the transmission input shaft and planetary gears to drive the vehicle down the road. Most torque converters have a “lockup clutch” that engages hydraulically when controlled by an electronic solenoid valve to physically couples the engine and transmission in higher gears to eliminate slippage for improved fuel economy. On some of the latest automatics, an electromechanical clutch is used to couple the transmission to the engine. The torque converter holds approximately

Most automatic transmissions are coupled to the engine with a torque converter, a fluid coupling mounted on the flywheel that transfers and multiplies engine torque to the transmission like a set of reduction gears. Inside the torque converter is a three-piece set of closely spaced blades (the “turbine, stator and impeller”). As the torque converter rotates, fluid is thrown from one set of blades against the other, pushing the blades connected to the transmission input shaft and planetary gears to drive the vehicle down the road. Most torque converters have a “lockup clutch” that engages hydraulically when controlled by an electronic solenoid valve to physically couples the engine and transmission in higher gears to eliminate slippage for improved fuel economy.

On some of the latest automatics, an electromechanical clutch is used to couple the transmission to the engine. The torque converter holds approximately one third of the total fluid required by the transmission. A bad converter will prevent the engine from accelerating normally, and may cause it to stall when the vehicle comes to a halt. Replacement torque converters with higher than stock stall speeds are available for performance applications.

A higher stall speed improves off the line acceleration but reduces fuel economy. Troubleshooting automatic transmission problems requires a scan tool to access diagnostic trouble codes, and a pressure gauge to monitor internal line pressure. If a transmission has an internal problem, it usually requires rebuilding or replacing the transmission.

Most transmissions are rebuilt by transmission specialists, though many individual components, such as filters, gaskets and seals, are available from aftermarket sources. Related items that may be needed when replacing a transmission include motor and transmission mounts, U-joints and CV-joints or halfshafts. Most transmission failures can be traced to fluid breakdown. Automatic Transmission Fluid (ATF) lubricates the transmission, and carries hydraulic pressure to shift gears and transfer engine torque inside the torque converter.

ATF is a lightweight mineral or synthetic oil that contains special additives and friction modifiers as specified by the vehicle manufacturer. Over time, ATF can oxidize, break down and cause the transmission to fail. Fluid changes can prolong the life of the transmission.Many newer vehicles have long-life ATF with a 100,000-mile or longer service life, but pulling a trailer, abusive driving, severe environmental conditions may cause the fluid to break down prematurely, requiring the fluid to be changed at lower mileage.

Different transmissions require different types of ATF. Many automakers have their own ATF requirements, and Using the wrong type of ATF can cause shift problems and may lead to transmission failure. If using a “universal” fluid, make sure it meets the specific requirements of the vehicle manufacturer.

The filter inside the transmission should also be replaced with the fluid. The filter is usually located inside the bottom transmission cover, and will require a new pan gasket, though on a few applications an easy-to-replace spin-on filter is used. Fluid leaks from a transmission may require replacing the output shaft and/or input shaft seals. The ATF oil cooler helps maintain the operating temperature of the fluid so it does not get too hot.

The ATF cooler is usually located inside the radiator. A short loop of pipe provides heat exchange between the fluid and coolant. A leak here can contaminate the fluid with coolant and vice versa. For towing or heavy-duty use, recommend the installation of an aftermarket auxiliary ATF cooler.

Most automatic transmissions are coupled to the engine with a torque converter, a fluid coupling mounted on the flywheel that transfers and multiplies engine torque to the transmission like a set of reduction gears. Inside the torque converter is a three-piece set of closely spaced blades (the “turbine, stator and impeller”). As the torque converter rotates, fluid is thrown from one set of blades against the other, pushing the blades connected to the transmission input shaft and planetary gears to drive the vehicle down the road. Most torque converters have a “lockup clutch” that engages hydraulically when controlled by an electronic solenoid valve to physically couples the engine and transmission in higher gears to eliminate slippage for improved fuel economy. On some of the latest automatics, an electromechanical clutch is used to couple the transmission to the engine. The torque converter holds approximately one third of the total fluid required by the transmission. A bad converter will prevent the engine from accelerating normally, and may cause it to stall when the vehicle comes to a halt. Replacement torque converters with higher than stock stall speeds are available for performance applications. A higher stall speed improves off the line acceleration but reduces fuel economy. Troubleshooting automatic transmission problems requires a scan tool to access diagnostic trouble codes, and a pressure gauge to monitor internal line pressure. If a transmission has an internal problem, it usually requires rebuilding or replacing the transmission. Most transmissions are rebuilt by transmission specialists, though many individual components, such as filters, gaskets and seals, are available from aftermarket sources. Related items that may be needed when replacing a transmission include motor and transmission mounts, U-joints and CV-joints or halfshafts. Most transmission failures can be traced to fluid breakdown. Automatic Transmission Fluid (ATF) lubricates the transmission, and carries hydraulic pressure to shift gears and transfer engine torque inside the torque converter. ATF is a lightweight mineral or synthetic oil that contains special additives and friction modifiers as specified by the vehicle manufacturer. Over time, ATF can oxidize, break down and cause the transmission to fail.

Most torque converters have a “lockup clutch” that engages hydraulically when controlled by an electronic solenoid valve to physically couples the engine and transmission in higher gears to eliminate slippage for improved fuel economy. On some of the latest automatics, an electromechanical clutch is used to couple the transmission to the engine. The torque converter holds approximately one third of the total fluid required by the transmission. A bad converter will prevent the engine from accelerating normally, and may cause it to stall when the vehicle comes to a halt. Replacement torque converters with higher than stock stall speeds are available for performance applications. A higher stall speed improves off the line acceleration but reduces fuel economy.

Troubleshooting automatic transmission problems requires a scan tool to access diagnostic trouble codes, and a pressure gauge to monitor internal line pressure. If a transmission has an internal problem, it usually requires rebuilding or replacing the transmission. Most transmissions are rebuilt by transmission specialists, though many individual components, such as filters, gaskets and seals, are available from aftermarket sources. Related items that may be needed when replacing a transmission include motor and transmission mounts, U-joints and CV-joints or halfshafts.

Most transmission failures can be traced to fluid breakdown. Automatic Transmission Fluid (ATF) lubricates the transmission, and carries hydraulic pressure to shift gears and transfer engine torque inside the torque converter. ATF is a lightweight mineral or synthetic oil that contains special additives and friction modifiers as specified by the vehicle manufacturer. Over time, ATF can oxidize, break down and cause the transmission to fail.

Most torque converters have a “lockup clutch” that engages hydraulically when controlled by an electronic solenoid valve to physically couples the engine and transmission in higher gears to eliminate slippage for improved fuel economy. On some of the latest automatics, an electromechanical clutch is used to couple the transmission to the engine. The torque converter holds approximately one third of the total fluid required by the transmission. A bad converter will prevent the engine from accelerating normally, and may cause it to stall when the vehicle comes to a halt. Replacement torque converters with higher than stock stall speeds are available for performance applications. A higher stall speed improves off the line acceleration but reduces fuel economy. Troubleshooting automatic transmission problems requires a scan tool to access diagnostic trouble codes, and a pressure gauge to monitor internal line pressure. If a transmission has an internal problem, it usually requires rebuilding or replacing the transmission. Most transmissions are rebuilt by transmission specialists, though many individual components, such as filters, gaskets and seals, are available from aftermarket sources. Related items that may be needed when replacing a transmission include motor and transmission mounts, U-joints and CV-joints or

Most transmissions are rebuilt by transmission specialists, though many individual components, such as filters, gaskets and seals, are available from aftermarket sources. Related items that may be needed when replacing a transmission include motor and transmission mounts, U-joints and CV-joints or halfshafts. Most transmission failures can be traced to fluid breakdown.

Automatic Transmission Fluid (ATF) lubricates the transmission, and carries hydraulic pressure to shift gears and transfer engine torque inside the torque converter. ATF is a lightweight mineral or synthetic oil that contains special additives and friction modifiers as specified by the vehicle manufacturer. Over time, ATF can oxidize, break down and cause the transmission to fail.

Troubleshooting automatic transmission problems requires a scan tool to access diagnostic trouble codes, and a pressure gauge to monitor internal line pressure. If a transmission has an internal problem, it usually requires rebuilding or replacing the transmission. Most transmissions are rebuilt by transmission specialists, though many individual components, such as filters, gaskets and seals, are available from aftermarket sources. Related items that may be needed when replacing a transmission include motor and transmission mounts, U-joints and CV-joints or halfshafts. Most transmission failures can be traced to fluid breakdown. Automatic Transmission Fluid (ATF) lubricates the

Most transmission failures can be traced to fluid breakdown. Automatic Transmission Fluid (ATF) lubricates the transmission, and carries hydraulic pressure to shift gears and transfer engine torque inside the torque converter. ATF is a lightweight mineral or synthetic oil that contains special additives and friction modifiers as specified by the vehicle manufacturer. Over time, ATF can oxidize, break down and cause the transmission to fail.

Most transmission failures can be traced to fluid breakdown. Automatic Transmission Fluid (ATF) lubricates the transmission, and carries hydraulic pressure to shift gears and transfer engine torque inside the torque converter. ATF is a lightweight mineral or synthetic oil that contains special additives and friction modifiers as specified by the vehicle manufacturer. Over time, ATF can oxidize, break down and cause the transmission to fail.

Most torque converters have a “lockup clutch” that engages hydraulically when controlled by an electronic solenoid valve to physically couples the engine and transmission in higher gears to eliminate slippage for improved fuel economy. On some of the latest automatics, an electromechanical clutch is used to couple the transmission to the engine. The torque converter holds approximately one third of the total fluid required by the transmission.

A bad converter will prevent the engine from accelerating normally, and may cause it to stall when the vehicle comes to a halt. Replacement torque converters with higher than stock stall speeds are available for performance applications. A higher stall speed improves off the line acceleration but reduces fuel economy. Troubleshooting automatic transmission problems requires a scan tool to access diagnostic trouble codes, and a pressure gauge to monitor internal line pressure. If a transmission has an internal problem, it usually requires rebuilding or replacing the transmission.

Most transmissions are rebuilt by transmission specialists, though many individual components, such as filters, gaskets and seals, are available from aftermarket sources. Related items that may be needed when replacing a transmission include motor and transmission mounts, U-joints and CV-joints or halfshafts. Most transmission failures can be traced to fluid breakdown.

Automatic Transmission Fluid (ATF) lubricates the transmission, and carries hydraulic pressure to shift gears and transfer engine torque inside the torque converter. ATF is a lightweight mineral or synthetic oil that contains special additives and friction modifiers as specified by the vehicle manufacturer. Over time, ATF can oxidize, break down and cause the transmission to fail.

Fluid changes can prolong the life of the transmission.Many newer vehicles have long-life ATF with a 100,000-mile or longer service life, but pulling a trailer, abusive driving, severe environmental conditions may cause the fluid to break down prematurely, requiring the fluid to be changed at lower mileage. Different transmissions require different types of ATF. Many automakers have their own ATF requirements, and Using the wrong type of ATF can cause shift problems and may lead to transmission failure. If using a “universal” fluid, make sure it meets the specific requirements of the vehicle manufacturer.

The filter inside the transmission should also be replaced with the fluid. The filter is usually located inside the bottom transmission cover, and will require a new pan gasket, though on a few applications an easy-to-replace spin-on filter is used. Fluid leaks from a transmission may require replacing the output shaft and/or input shaft seals. The ATF oil cooler helps maintain the operating temperature of the fluid so it does not get too hot. The ATF cooler is usually located inside the radiator. A short loop of pipe provides heat exchange between the fluid and coolant. A leak here can contaminate the fluid with coolant and vice versa. For towing or heavy-duty use, recommend the installation of an aftermarket auxiliary ATF cooler.

Most torque converters have a “lockup clutch” that engages hydraulically when controlled by an electronic solenoid valve to physically couples the engine and transmission in higher gears to eliminate slippage for improved fuel economy. On some of the latest automatics, an electromechanical clutch is used to couple the transmission to the engine. The torque converter holds approximately one third of the total fluid required by the transmission. A bad converter will prevent the engine from accelerating normally, and may cause it to stall when the vehicle comes to a halt. Replacement torque converters with higher than stock stall speeds are available for performance applications.

A higher stall speed improves off the line acceleration but reduces fuel economy. Troubleshooting automatic transmission problems requires a scan tool to access diagnostic trouble codes, and a pressure gauge to monitor internal line pressure. If a transmission has an internal problem, it usually requires rebuilding or replacing the transmission. Most transmissions are rebuilt by transmission specialists, though many individual components, such as filters, gaskets and seals, are available from aftermarket sources. Related items that may be needed when replacing a transmission include motor and transmission mounts, U-joints and CV-joints or halfshafts.

Most transmission failures can be traced to fluid breakdown. Automatic Transmission Fluid (ATF) lubricates the transmission, and carries hydraulic pressure to shift gears and transfer engine torque inside the torque converter. ATF is a lightweight mineral or synthetic oil that contains special additives and friction modifiers as specified by the vehicle manufacturer. Over time, ATF can oxidize, break down and cause the transmission to fail. Fluid changes can prolong the life of the transmission.Many newer vehicles have long-life ATF with a 100,000-mile or longer service life, but pulling a trailer, abusive driving, severe environmental conditions may cause the fluid to break down prematurely, requiring the fluid to be changed at lower mileage.

Different transmissions require different types of ATF. Many automakers have their own ATF requirements, and Using the wrong type of ATF can cause shift problems and may lead to transmission failure. If using a “universal” fluid, make sure it meets the specific requirements of the vehicle manufacturer. The filter inside the transmission should also be replaced with the fluid. The filter is usually located inside the bottom transmission cover, and will require a new pan gasket, though on a few applications an easy-to-replace spin-on filter is used. Fluid leaks from a transmission may require replacing the output shaft and/or input shaft seals.

The ATF oil cooler helps maintain the operating temperature of the fluid so it does not get too hot. The ATF cooler is usually located inside the radiator. A short loop of pipe provides heat exchange between the fluid and coolant. A leak here can contaminate the fluid with coolant and vice versa. For towing or heavy-duty use, recommend the installation of an aftermarket auxiliary ATF cooler.