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Automatic Transmission/Transaxle: Description and Operation: Overview





Transmission Description

OVERVIEW
The ZF 6HP26 transmission is an electronically controlled, six speed unit. The transmission is manufactured by ZF Transmissions GmbH in Saarbrucken, Germany.
This transmission represents the latest in automatic transmission technology and incorporates new features to enhance the transmission functionality:
- The hydraulic and electronic control elements of the transmission, including the TCM (transmission control module) , are incorporated in a single unit located inside the transmission and is known as 'Mechatronic'
- Another new strategy is Adaptive Shift Strategy (ASIS). ASIS represents the continuous adaptation of shift changes to suit the driving style of the driver which can vary from sporting to economical.
On supercharged models, the transmission used is an uprated derivative of the 6HP26 transmission used in the 4.2L naturally aspirated model. The uprated transmission includes additional clutch plates to enable the transmission to manage the additional power output of the supercharged engine.
The 6HP26 transmission has the following features:
- Designed to be maintenance free
- Transmission fluid is 'fill for life'
- The torque converter features a controlled slip feature with electronically regulated control of lock-up, creating a smooth transition to the fully locked condition
- Shift programs controlled by the TCM (transmission control module)
- Connected to the ECM (engine control module) via the High Speed CAN (controller area network) bus for communications
- Uses a High Speed CAN (controller area network) bus and a 'K' Line (early build vehicles only) connection to the diagnostic socket for diagnostic connection
- Default mode if major faults occur
- Diagnostics available from the TCM (transmission control module) via the high speed CAN (controller area network) bus.
The gearbox comprises the main casing which houses all of the transmission components. The main case also incorporates an integral bell housing. A fluid pan is bolted to the lower face of the main case and is secured with bolts. The fluid pan is sealed to the main case with a gasket. Removal of the fluid pan allows access to the Mechatronic valve block. The fluid pan has a magnet located around the drain plug which collects any metallic particles present in the transmission fluid. A fluid filter is located inside the fluid pan. If the transmission fluid becomes contaminated or after any service work, the fluid pan with integral filter must be replaced.
The integral bell housing provides protection for the torque converter assembly and also provides the attachment for the gearbox to the engine cylinder block. The torque converter is a non-serviceable assembly which also contains the lock-up clutch mechanism.
The torque converter drives a crescent type pump via drive tangs. The fluid pump is located in the main case, behind the torque converter.
The main case contains the following major components:
- Input shaft
- Output shaft
- Mechatronic valve block which contains the solenoids, speed sensors and the TCM (transmission control module)
- Three rotating multiplate drive clutches
- Two fixed multiplate brake clutches
- A single planetary gear train and a double planetary gear train.