Rear Differential System Description

Rear Differential System Description

VTM-4 System

Outline

This vehicle is equipped with a rear differential system called the variable torque management 4WD (VTM-4) system. The VTM-4 control unit controls the current flowing through electromagnetic coils to engage and disengage the right and left clutches in the rear differential assembly.

The operation of the VTM-4 system consists of the following functions:

- Vehicle acceleration torque control (VATC)
- Limited slip differential (LSD)
- Lock control

Operation

These functions automatically combine to distribute driving torque between the front and rear wheels when the vehicle is being accelerated or when wheels are slipping. When the vehicle speed is about 18 mph (30 km/h) or below, and the transmission is in R, 2, or 1, the system will manually engage the rear differential clutches when the VTM-4 LOCK button is pressed. By design, in lock mode, the torque is reduced gradually at speeds above 6 mph (10 km/h) to minimize the load on the 4WD system.

The VTM-4 control unit has a fail-safe function and a self-diagnosis function.

- VATC (Vehicle Acceleration Torque Control) Control
The torque to be delivered to the rear wheels is calculated based on the acceleration of the vehicle calculated in the VTM-4 control unit.

- LSD (Limited Slip Differential) Control
The torque to be delivered to the rear wheels is calculated based on the differences in speed and acceleration between the front and rear wheels.

- LOCK Control
Rear differential clutch lock control is done by pushing the VTM-4 LOCK button manually when the shift lever is in R, 1, or 2.

Electronic Control System

VTM-4 Control Unit Electrical Connections

VTM-4 Control Unit Inputs and Outputs

The VTM-4 control unit terminal voltage and measuring conditions for the VTM-4 inputs and outputs test are done with the VTM-4 connectors connected.