Jaguar XJ (X350). Manual — part 1038

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 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

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.

Upshifts

Transmission upshifting is controlled by the TCM. The TCM receives inputs from various engine or

vehicle sensors and driver demands to control shift scheduling, shift feel and torque converter clutch

(TCC) operation.

The TCM has an adaptive learn strategy to electronically control the transmission which will

automatically adjust the shift feel.

Downshifts

Under certain conditions the transmission will downshift automatically to a lower gear range

(without moving the gearshift lever). There are three categories of automatic downshifts, coastdown,

torque demand and forced or kickdown shifts.

Coastdown

The coastdown downshift occurs when the vehicle is coasting down to a stop.

Torque Demand

The torque demand downshift occurs (automatically) during part throttle acceleration when the

demand for torque is greater than the engine can provide at that gear ratio. If applied, the

transmission will disengage the TCC to provide added acceleration.

Kickdown

For maximum acceleration, the driver can force a downshift by pressing the accelerator pedal to the

floor. A forced downshift into a lower gear is possible below calibrated speeds. Specifications for

downshift speeds are subject to variations due to tire size and engine and transmission calibration

requirements.

Range Selection

Depending on the vehicle options selected the transmission range selector may have different range

positions.

The standard range selector has eight positions: P, R, N, D, 5, 4, 3 and 2.

J-Gate Range Selection

"P"

In the PARK position:

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there is no power flow through the transmission.

the parking pawl locks the output shaft to the case.

the engine may be started.

the ignition key may be removed.

"R"

In the REVERSE position:

the vehicle may be operated in a rearward direction, at a reduced gear ratio.

backup lamps are illuminated.

"N"

In the NEUTRAL position:

there is no power flow through the transmission.

the output shaft is not held and is free to turn.

the engine may be started.

"D"

DRIVE is the normal position for most forward driving.

The D position provides:

automatic shift 1-6 and 6-1.

apply and release of the torque converter clutch.

maximum fuel economy during normal operation.

engine braking in 6th gear.

"5"

The 5 position provides:

automatic shift 1-5 and 5-1.

apply and release of the torque converter clutch.

engine braking in 5th gear.

"4"

The 4 position provides:

automatic shift 1-4 and 4-1.

apply and release of the torque converter clutch.

engine braking in 4th gear.

"3"

The 3 position provides:

automatic shift 1-3 and 3-1.

engine braking in 3rd gear.

"2"

The 2 position provides:

automatic shift 1-2 and 2-1.

engine braking in 2nd gear.

"S"

The sport mode switch:

allows the driver to select or de-select the automatic transmission sport mode.

allows the automatic transmission to operate normally when the sport mode is selected, but

under acceleration the gear shift points are extended to make full use of the engine's power
reserves.

allows the driver to drive the vehicle in the "D" position with the full automatic transmission shift

or manually shift gears in the "second, third, fourth and fifth" positions.

is illuminated when Sport mode is selected.

communicates with the TCM through the CAN network to show the sport mode switch status.

Torque converter

The torque converter is a three element unit containing a single plate lock up clutch. The lock up

clutch can be controlled and engaged in any gear 1 to 6. The clutch is applied by removing

transmission fluid pressure from one side of the plate. The torque converter transmits and multiplies

torque. The torque converter is a three-element device:

impeller assembly

turbine assembly

reactor assembly

The standard torque converter components operate as follows:

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