Transaxle Description
Transaxle DescriptionThe automatic transmission used in the vehicle is a new development.
It is a fully automatic, electronically controlled 4-speed transmission designed for front-wheel drive vehicles.
Its abbreviated designation 4F27E means:
^ 4 - 4-speed transmission
^ F - front-wheel drive
^ 27 - originally designed for maximum input torque after torque converter: 365 Nm (270 ft. lbs.)
^ E - fully electronically controlled
The individual ratios are achieved through 2 planetary gear sets, connected one behind the other.
The individual components of the planetary gear sets are driven or held by means of 3 multi-plate clutches, a multi-plate brake, a brake band and a roller one-way clutch.
The torque is transmitted to the final drive assembly through an intermediate gear stage.
MERCON V is the fluid specified for the 4F27E transmission. The fluid is changed as directed by the Scheduled Maintenance Guide that is supplied with the vehicle.
The manual selector lever gives the driver a choice of P, R, N, 1, 2 and D.
In drive range "D" it is also possible to operate an overdrive (O/D) switch on the manual selector lever to prevent the transmission from shifting into 4th gear. The default gear for this transmission is 3rd gear.
To minimize fuel consumption, the torque converter lock-up clutch is closed by the powertrain control module (PCM) in 3rd and 4th gears depending on the throttle position and vehicle speed.
The transmission has electronic synchronous shift control (ESSC), which guarantees extremely smooth gear shifting over the entire life of the transmission.
A hydraulic emergency operating program maintains limited operation in the event of failure of important electrical components.
The transmission can be tested using FDS2000, NGS or WDS through the data link connector (DLC) in the passenger compartment.
Valve Body
Valve Body:
The valve body contains 6 solenoid valves:
^ three pulse width modulation (PWM) solenoid valves,
^ two shift solenoid (on/off) valves,
^ one main regulating valve (variable force solenoid).
The individual clutches and bands are supplied pressure from the PWM solenoid valves and the shift solenoid (on/off) valves and thus the gears are shifted.
The PWM solenoid valves allow direct actuation of the clutches and bands to make sure extremely smooth gear shifting through precise pressure regulation.
The shift solenoid (on/off) valves switch the hydraulic path to the clutches and bands, reducing the number of required modulating valves.
The main regulating valve (variable force solenoid) makes sure that sufficient hydraulic pressure is available in all operating conditions.
PWM solenoid valves 1-3
PWM solenoid valves 1, 2 and 3 control the pressure to the bands and clutches.
Shift solenoid (on/off) valves 1 and 2
The shift solenoid (on/off) valves switch the different oil passages in the valve body to direct the pressure to the individual clutches and bands.
The use of the shift solenoid valves are needed for direct actuation of the individual clutches and bands.
Main regulating valve
The main regulating valve (variable force solenoid) controls the required main line pressure for the individual transmission ranges.
The main line pressure is controlled dependent on the current engine load.
Internal Shift Mechanism
Internal Shift Mechanism:
The shift lever is secured on a square on the manual shaft. Axial movement of the selector lever cable is changed into rotation of the manual shaft.
In the transmission, the manual shaft operates the parking pawl engaging lever and the actuating lever of the manual valve.
The manual valve, a valve operated entirely manually, is moved by means of the manual valve actuating lever in the valve body.
The manual valve guarantees the functions during hydraulic emergency operation.
External Shift Mechanism
External Shift Mechanism:
The transmission end of the manual selector lever cable is attached to a ball on the lever on the manual shaft.
The cable abutments are secured to the transmission housing, and then to the bracket of the manual selector lever.
The adjuster for the manual selector lever cable is located at the transmission side of the sheath.
At the manual selector lever end the cable is clipped onto a ball.
Intermediate Gear Stage and Final Drive Assembly
Intermediate Gear Stage and Final Drive Assembly (Part 1):
Intermediate Gear Stage and Final Drive Assembly (Part 2):
The final drive input gear is splined to the planet carrier of the front planetary gear set and drives the transfer shaft input gear of the intermediate gear stage.
The transfer shaft output gear of the intermediate gear stage drives the final drive assembly.
The torque is transmitted to the halfshafts through the final drive assembly.
The differential offsets differences in speed of rotation of the halfshafts.
The intermediate gear stage is designed so that the final drive ratio can be adapted to requirements when the automatic transmission is used in conjunction with different engines.