General

GENERAL

Used in the transfer is the VTD (Variable Torque Distribution) system which combines a compound planetary gear type center differential installed in the transfer case behind the transmission and a hydraulically operated multi-plate differential action limiting device (LSD) located between the output shafts of the center differential. Differential action limiting control is performed by the TCM according to driving and road surface conditions.

The input torque is transmitted to the 1st sun gear of the center differential through the intermediate shaft. From the 1st sun gear, the torque is transmitted through the 1st pinion to the output carrier in the front wheel output shaft, and through the 2nd pinion to the 2nd sun gear in the rear wheel output shaft.

The center differential performs the differential functions of absorbing the speed difference between the front and rear wheels and also distributes drive forces to the front and rear wheels at a predetermined ratio. In normal conditions (when pressure is not applied to the multi-plate clutch), the drive force distribution ratio is 45.7 % to the front wheels and 54.3 % to the rear wheels. The hydraulic multi-plate clutch connected in parallel with the center differential between the carrier and 2nd sun gear functions as a differential action limiting device (LSD) and also as a device that controls torque distribution according to driving conditions.

Differential action limiting control is performed as a "torque responsive control", where control is based on the input torque to the transfer as calculated from the engine torque, torque converter characteristics, gear ratio, etc.The LSD clutch is controlled by the hydraulic pressure regulated by the transfer valve in the transmission hydraulic control valve assembly, as a result of the TCM directly controlling the linear solenoid. The torque distribution ratio to front and rear wheels changes from 45.7:54.3 to direct connection, in accordance with the hydraulic pressure acting on the piston.

The speed of the front and rear wheels determine the basic signals for the differential action limiting control. The rear wheel speed is detected by the sensor installed above the rear drive shaft, and the front wheel speed is detected by the sensor on the parking gear above the reduction gear.