Transmission (07.00)

Transmission (07.00)

Automatic Transaxle (07.01)

Description

The ZF 6HP26 automatic gearbox has the following features:

• Six forward speeds / One reverse
• A torque converter with an integral converter lock-up clutch
• Electronic shift and pressure controls
• A single planetary gear set
• A double planetary gear set
• Two fixed multi-disc brakes
• Three multi-plate clutches

All hydraulic functions are directed by electronic solenoids to control:

• Engagement feel
• Shift feel
• Shift scheduling
• Modulated torque converter clutch (TCC) applications
• Engine braking utilizing the coast clutch

The ZF 6HP26 Automatic Transmission is a six speed electronically controlled transmission comprising the basic elements of:

• A Mechatronik module (Transmission Control Module (TCM) and main control valve body assembly)
• A torque converter
• One solenoid valve and six pressure regulators

Gear selection is achieved by the control of the transmission oil flow to operate various internal clutches. The TCM operates the electrical components and provides for the control of gear selection shift pressure which increases refinement and torque converter slip control.

In the event of a system fault the TCM also provides for Failure Mode Effect Management (FMEM) to maintain maximum functional operation of the transmission with a minimum reduction in driver, passenger or vehicle safety. In the event of a total loss of control or electrical power the basic transmission functions Park, Reverse, Neutral and Drive are retained. Also 3rd or 5th gear is retained by the hydraulic system, the gear retained is dependant upon the gear selected at time of the failure.

The transmission also contains turbine and output shaft speed sensors, an internal P, R, N, D selector position sensor, and a transmission oil temperature sensor. The TCM also requires information from the shift selector module to determine when the driver has initiated manual gear selection. The TCM communicates with other electronic control modules by the controller area network (CAN).

The TCM also provides for legislated transmission diagnostics, which meet the requirements of CARB OBDII legislation, monitoring all components, which may effect vehicle emissions. Additional diagnostic functions are also supported to ensure fast repairs of all failures in the service environment.

Engine power transfers to the transmission by a torque converter with integral converter lock-up clutch. Six forward gears and one reverse gear are obtained from a single planetary set followed by a double planetary set also known as lepelletier-type gear sets, these gear sets make it possible to obtain the six forward gears.

Cooling

The Auto transmission has an external cooling circuit which prevents overheating of the transmission oil. A pump mounted in the gearbox, working on engine speed variation, pumps the transmission oil around the radiator and back to the transmission.

A thermostat (Wax / Poppet type), close to the gearbox inlet / outlet, controls the oil temperature, operating at a range of 74°C - 88°C.

Mechatronik module

The Mechatronik module is located in the sump of the automatic gearbox. It contains electrical actuators and sensors as well as hydraulic valves which, acting in conjunction with the TCM, perform gear changes.

The electromechanical components are arranged in such a way that they may be replaced while the automatic gearbox is installed in the vehicle.

(Refer to 'Automatic Control System (07.05)', page 7-4-1)