Transmission Description
The ZF 6HP26 automatic transmission has been developed for vehicles with an engine torque of up to 600 Newton-meters (Nm). This transmission uses planetary gears with hydraulic-electronic control. The transmission control module (TCM) and the main control valve body units form a composite element that is installed as a single unit inside the automatic transmission.
The 6HP26 has the following features:
- Six forward speeds.
- 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.
Engine power reaches the transmission by a torque converter with integral converter lock up clutch. The 6 forward gears and 1 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 6 forward gears.
The 6HP26 Automatic Transmission is a six speed electronically controlled transmission comprising the basic elements of a TCM and main control valve body unit, a torque converter, one solenoid valve and six pressure regulators. Gear selection is achieved by the control of Automatic Transmission Fluid (ATF) 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 defendant 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 shaft position sensor, and a transmission fluid temperature sensor. The TCM also requires information from the J-Gate 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.