Super Select is the brand name of a four-wheel drive system produced by Mitsubishi Motors, used worldwide except for North America, where it is known as Active-Trac. It was first introduced in 1991 with the then-new second generation of the Mitsubishi Pajero.

The system offers a choice of four rear- or four-wheel driving modes, selected using a lever mounted alongside the gear shift, and can be changed while the vehicle is in motion. In 2H mode the front axle is disconnected and the vehicle is rear-wheel drive. Reduced frictional losses in the powertrain mean that fuel economy improves while noise levels are reduced. 4H is a part-time four-wheel drive mode using a viscous coupling unit (VCU) and center differential to direct drive to the front wheels when the rear axle loses traction, and is capable of handling a wide variety of road conditions and speeds. 4HLc locks the center differential to provide extra traction for sandy, snowy or poorly surfaced roads in "high range" mode, while 4LLc, the "low range" mode, also offers a much lower gearing, providing the maximum amount of traction. Changing between 4HLc and 4LLc is only possible with the vehicle stationary.

The system is used on Mitsubishi's Pajero iO mini SUV, while its larger Pajero, Challenger, Triton and Delica models use a more complex system dubbed Super Select 4WD II (SS4-II). In most respects the two are the same, although the torque-split in SS4-II is 33/67 front/rear, meaning two thirds of the torque is channelled to the rear axle. In Super Select (SS4i) the torque-split is an equal 50/50. SS4-II also offers an option to lock the rear differential, offering greater traction to the rear axle.

One of the notable features about the Shogun Pinin is that although a compact 4x4, it is, unlike most rivals, available with a fully fledged 4WD system. This makes it a true off-roader and not merely a 'soft-roader' that will struggle at the first bumpy track or steep hill. The hardware used in the 2.0-litre Pinins is SS4-i (SS standing for Super Select), a four-mode system operated from a selector lever situated between the front seats.

The mode for everyday driving is, as with Easy Select, '2H'. Here, drive is to the rear wheels only, on the basis that on good road surfaces you don't need anything more.

The first 4WD setting is '4H', which adds drive to the front wheels, and like Easy Select it allows shift-on-the-fly. But one important difference is that you can use 4H on dry roads without fear of transmission wind-up.

Indeed, in 4H SS4-i is in 'thinking' mode, because although you've selected 4WD, power is still only fed to the rear wheels until surface conditions dictate that the front wheels need it too.

This is achieved via a device in the centre differential known as a viscous-coupling unit (VCU), which senses when the rear wheels are losing grip, and instantly feeds drive to the front wheels so that they can help with traction. This could happen when, say, you hit a patch of ice on the road.

The benefit is that the vehicle is only using 4WD when it really has to, and so is always running as smoothly as possible as well as optimising fuel economy.

While the above mode is suitable for driving in a mix of road conditions, '4HLc' is intended for slippery off-road terrain, wet grass for example. When 4HLc is selected, the VCU is bypassed and drive to the front and rear axles is locked up, which takes out any speed differences between the front and rear wheels. Thus, provided all four wheels are still on the ground the Shogun Pinin should keep moving.

The '4LLc' mode is the low-ratio version of 4HLc, with ultra-low overall gearing allowing you to use high revs at low speed in order to get the most traction. Changing between 4HLc and 4LLc is only possible with the vehicle stationary.

The 1.8-litre models in the Pinin range use a simpler 4WD set-up, one where the driver doesn't have to decide anything. Four-wheel-drive is permanently engaged, with the centre differential splitting engine torque in the ratio 50/50 front/rear.

The most impressive 4WD system in the Mitsubishi armoury is SS4-II, used in the Shogun. It offers the same four modes as SS4-i, except it overlays an increased level of sophistication, which eases selection and improves on-road driving characteristics.

The 2H function is unchanged over SS4-i, but in 4H the VCU splits the engine torque in the ratio 33/67 front/rear as opposed to the 50/50 distribution in SS4-i. The benefit here is that the bulk of the power going to the rear wheels gives better balanced on-road handling, making the Shogun feel more sporty through corners. However when slippery road or off-road conditions demand, the VCU will automatically split the torque accordingly, from 33/67 front/rear to 50/50 front/rear.

The 4HLc and 4LLc work in the same way as in the Pinin, being the two settings for off-roading. However the driver also has the option of locking the rear differential, for side-to-side locking of the rear axle.

Thanks to clever electronics, SS4-II offers a simple, effortless engagement of the modes. To switch between them, the driver slides a lever on the transmission tunnel through the four positions, with a press-down action preventing accidental selection.

See also: 4x4, AWD, 4WD