Manual Transmission/Transaxle: Description and Operation
Manual Transmission Description and Operation
Manual transmissions are identified by the number of forward gears and the measured distance between the centerline of the output shaft and the counter gear.
The 6-speed manual transmission (RPO M12), incorporates the following features:
^ An aluminum case
^ Fully synchronized gearing with an enhanced synchronizer cone arrangement:
- Triple-cone: FIRST, SECOND
- Double-cone: THIRD, FOURTH, FIFTH, SIXTH
- Single-cone: REVERSE
^ An internal shift rail mechanism
^ A remote transmission shift control mounted forward of the transmission
^ An external transmission shift rod enabling the forward mount location of the transmission shift control
^ An extended-length transmission output shaft mating directly to the rear axle drive pinion, in the rear of the differential housing
^ Tapered roller bearings supporting the mainshaft and countershaft
^ Caged roller bearings under all speed gears
^ Solenoid inhibit of SECOND and THIRD gears
^ Solenoid inhibit of REVERSE gear during predefined forward motion
These features combine to yield a rugged, reliable system capable of handling input torques of up to 610 Nm (450 ft. lbs.) for the M12.
The gear ratios are as follows:
Gear Select - Skip Shift
To ensure good fuel economy and compliance with federal fuel economy standards, SECOND and THIRD gears are inhibited when shifting out of FIRST gear under the following conditions:
^ Coolant temperature is above 76°C (169°F).
^ Vehicle speed is 24 - 31 km/h (15 - 19 mph).
^ Throttle is opened 21 percent or less.
Reverse Lockout
A reverse lockout system, consisting of a reverse lockout solenoid which operates a reverse lockout mechanism, is utilized to prevent shifting into REVERSE gear when the vehicle is moving forward at a speed of 5 km/h (3 mph) or more.
Description and Operation
Reverse Inhibit Description and Operation
The reverse inhibit solenoid is a safety feature which prevents an inadvertent shift into reverse at speeds above 5 km/h (3 mph). The system consist of the following components:
^ The engine control module (ECM)
^ The transmission control module (TCM)
^ The reverse inhibit solenoid
With the ignition ON battery voltage is supplied directly to the reverse inhibit solenoid. At forward speeds above 5 km/h (3 mph) the PCM grounds the control circuit of the reverse inhibit solenoid. This energizes the solenoid and mechanically blocks the shift lever from going into the REVERSE position.
Description and Operation
Skip Shift Description and Operation
The skip shift solenoid is a performance feature which forces the driver to shift from first gear to fourth gear during light acceleration and low engine load conditions. This feature is used to ensure good fuel economy and compliance with federal economy standards. The skip shift system consist of the following components:
^ The powertrain control module (PCM)
^ The skip shift solenoid
^ The skip shift lamp
With the ignition ON, battery voltage is supplied directly to the skip shift solenoid. The PCM controls the solenoid by grounding the control circuit. When the skip shift system is active the PCM also grounds the control circuit of the skip shift lamp. The lamp illuminates to inform the driver that the 1-4 skip shift is engaged. The PCM determines when the skip shift system is active when the following parameters are met:
^ The vehicle speed is between 24 - 31 km/h (15 - 19 mph).
^ The engine coolant temperature (ECT) is greater than 77°C (171°F).
^ The barometric pressure (BARO) is greater than 76 kPa.
^ The accelerator pedal position (APP) is less than 26 percent.
When the conditions are met the PCM grounds the skip shift solenoid control circuit. This energizes the skip shift solenoid and mechanically blocks the gear shift lever from going into the second or third gear positions. When the driver pulls back on the shift lever with the system enabled, the transmission will go into fourth gear.
When the conditions for skip shift engagement are no longer met the PCM disables the skip shift solenoid, allowing the driver to use second and third gears.
Once the skip shift solenoid is enabled the system will not be re-enabled until the vehicle speed returns to 0 km/h (0 mph) and the conditions for enabling skip shift solenoid are met.