Other Systems for 4WD (4 wheel drive vehicles) 1 of 2


1. Free wheel hub

These are generally used on the front wheels of FR based part-time 4WD vehicles. This system uses clutch mechanisms to connect and disconnect the wheel and axle shaft. In 2WD mode, the front wheels transmit rotation to the front axle, front differential, and propeller shaft. This causes vibration and noise in the vehicle and lowers fuel efficiency. Thus, on unpaved roads, bad roads, and snowy roads, the free wheel hub is locked with 4WD mode, but on normal roads and high-speed roads, the free wheel hub is freed with 2WD mode. The types for switching the hub between “LOCK” and “FREE” are the manual type, which must be operated from outside the vehicle, and the automatic type, which can be switched automatically. There are also dual types that combine the manual type and the automatic type.

HINT: When the transfer is in 4WD, the hub must not be “FREE”.

NOTICE: The automatic type can only be switched when moving straight ahead. Check the Owner’s Manual carefully before switching.

2. ADD (Automatic Disconnecting Differential)

This is the front differential and contains a mechanism that connects/disconnects the axle shaft to which power is not transmitted when a part-time 4WD vehicle is in 2WD according to whether the transfer is switched to 2WD or 4WD. An ADD connects/disconnects the left or right axle shaft with an actuator linked to the switching of the transfer, so there is no need to switch with a free wheel hub. Further, in order to make it possible to switch from 2WD to 4WD even while running, the transfer has a synchronization mechanism for starting up the rotation of the drive system that is stopped during 2WD. Also, there is a one-touch 2-4 selector (push-button switch) or 4WD control switch inside the vehicle.

A-TRAC (Active Traction Control) System

During rugged off-road driving, this function controls the engine output and the brake fluid pressure that is applied to the slipping wheel, and distributes the drive force that would have been lost through the slippage to the remaining wheels in order to achieve a LSD effect. As a result, the vehicle’s off-road drivability and ability to free itself from the mogul have been increased.

Braking Force Test

1. Vehicle speed: below 0.5 km/h (0.3 mph)

When doing low-speed type brake tester measurements, observe the following instructions.

(1) Position the wheels to be tested (front or rear) on the tester.

(2) Put the center differential in Free position. Mechanical locking type:

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