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 N·m (450 lb ft) for the M12.
The gear ratios are as follows:
Gear | M12 Ratio (:1) |
|---|---|
FIRST | 2.97 |
SECOND | 2.07 |
THIRD | 1.43 |
FOURTH | 1.00 |
FIFTH | 0.84 |
SIXTH | 0.57 |
REVERSE | 3.28 |
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.
