System Description: Notes

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 currents 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

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 switch 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, a self-diagnosis function, and a provision to communicate with the HDS.

• VATC 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.

  Fig 2: Calculating Amount Of Torque Delivered To Rear Wheels (VATC Control)

  Courtesy of AMERICAN HONDA MOTOR CO., INC.
• LSD 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.

  Fig 3: Calculating Amount Of Torque Delivered To Rear Wheels (LSD Control)

  Courtesy of AMERICAN HONDA MOTOR CO., INC.
• LOCK Control

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

  Fig 4: Identifying Differential Clutch Lock Control Graph

  Courtesy of AMERICAN HONDA MOTOR CO., INC.