The 2003 Mitsubishi Shogun - Transmissions | Part Five


Motorway, open road and off-road driving have all been taken into consideration in the Shogun’s manual and automatic gear boxes which are at the forefront of the 4x4 market and have a fifth gear which acts more as an overdrive ratio.

The INVECS-II learning 5-speed automatic transmission with Sports Mode is available on many Shogun models, combining the appeal of a manual transmission with the convenience of an automatic gearbox. By offering two systems in one in this way, the driver has the convenience of automatic transmission when required yet is able to exercise more control when appropriate and realise the full potential of the engine.

INVECS-II has a transmission computer which monitors engine speed to gear box speed providing optimum and smooth gear changes, and Adaptive Shift Control technology allows the computer to record each individual’s driving pattern in order to adapt gear change timings to suit the driver’s style.

To engage Sports Mode, the gear lever is slid from ‘D’ into the adjacent gate. Then, moving the lever forward to ‘+’ changes up a gear, and backwards to ‘-’ changes down a gear. Drivers can still experience the advantages of double shifting by moving the shift lever twice in rapid succession, and to prevent the stress of constantly changing gear when driving around the town, the transmission automatically reverts to first gear when stationary.

When being driven in Automatic mode the INVECS-II transmission has the ability to learn and adapt to the way each individual drives by seamlessly switching between two logic control programmes. In Optimum Shift Control, the computer monitors the gear position, vehicle speed and foot braking then selects the right gear for the right time using its sophisticated control logic brain – with the advantage of avoiding awkward gear selection in tricky driving situations.

Building on the reputation of its SS4-I Super Select four-wheel drive system, Mitsubishi has further refined its technology and introduced SS4-II, which features a constant mesh torque transfer unit and centre differential with planetary gears and a VCU (Viscous Coupling Unit).

The SS4-II’s centre differential has been redesigned to accommodate planetary gears which moves away from the previous 50% - 50% split to a desirable 33% - 67% power distribution in 4H mode. The VCU transfers up to 50% of the torque to the front wheels if the rear wheels start losing traction and the centre differential locks for even more traction.

An electronically controlled transfer lever makes shifting between 2WD and 4WD modes even easier – with the driver having to press the lever down before it can be moved forward or back to prevent accidental operation.

The SS4-II has four operating modes:

  • 2H - 2WD high range provides smooth, quiet economical performance for ordinary town or motorway driving. In this mode, power is transferred entirely to the rear wheels and drivers can switch to 4H just by pushing the transfer lever down and into the 4H position at speeds of up to 62mph. To return to the 2H mode, the process is reversed and can be accomplished at any speed.
  • 4H - 4WD high range is ideal for safe, high speed driving in variable weather conditions. In this mode there is a 33% - 67% front/rear torque split as standard. However, if the speed difference between the front and rear wheels increases, the VCU operates to limit the centre differential action altering the torque split to 50% - 50% front/rear wheel drive. Transfer from 4H to 4HLc is possible at speeds of up to 62mph and, again, returning to 4H can be carried out at any speed.
  • 4HLc - 4WD high range with locked VCU provides traction on low grip surfaces such as sand and snow. This mode results in a 50% - 50% front/rear torque split. It transfers power to the front, bypassing the VCU. Transfer to 4LLc can only be done when the vehicle is stationary.
  • 4LLc - 4WD low range with locked VCU allows drivers to tackle extreme terrain such as snow, mud or sand covered slopes. The locked centre differential sends torque forward, bypassing the VCU, via a high-low transfer, counter gear, differential lock hub, and a linked plate chain. The transfer gear ratio of 1.9:1 is almost twice that of 4HLc mode allowing the Shogun to be able to deal with the trickiest of off-road conditions.

For added traction, a rear differential lock with a helical-geared LSD (limited slip differential) is also fitted.

continues... | Part Six
Published 22 December 2002 Melanie Carter

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