The described vehicles use one of two types of transfer case. Electric shift vehicles have the New Venture Gear NVG 226 transfer case. The electric shift transfer case has five modes: 2WD Overdrive, 4WD Overdrive, 4WD Low, Neutral and Automatic 4WD (A4WD).
Also, the described vehicles can use a single-speed automatic transfer case NVG 126. This box is constantly engaged in automatic all-wheel drive mode.
It is not recommended to carry out repair procedures on the transfer case yourself. It should be noted that repairs are extremely difficult to perform without the use of special equipment and devices. Moreover, purchasing and installing a remanufactured replacement transfer case may be more economically feasible than repairing an existing unit yourself, since repairs require inspecting, adjusting, and replacing many parts and components, as described in this chapter.
Controlled all-wheel drive system (S4WD)
This system allows you to choose one of four modes (upshift with two-wheel drive, upshift all-wheel drive, downshift all-wheel drive, neutral position), as well as additional (fifth) automatic all-wheel drive mode (A4WD). Switching modes occurs under electronic control.
When selecting one of the modes (when operating the switch located on the instrument panel) the transfer case switching unit receives a corresponding signal, and the rocker is turned by a servomotor (clockwise or counterclockwise). Thus, the transfer case switches to the required mode. After switching on a certain transfer case mode, a signal to turn on the front axle is received from the transmission control unit. The transfer case transmitting device, located on the servomotor, serves to transmit a signal corresponding to the position of the rocker to the transmission control unit. Also in the transfer case there is a servomotor locking device, which ensures fixation of the selected mode. When the A4WD button is pressed, the servo locking device remains in adaptive mode, so it can be unlocked or locked according to whether the transfer case switching unit accepts two-wheel drive or four-wheel drive.
When the automatic all-wheel drive mode is turned on (A4WD) The box goes into overdrive mode with all-wheel drive, but at the same time the connection of its internal clutch varies depending on changes in road conditions. When signals indicating wheel slippage are received in the transfer case switching unit (signals come from vehicle speed sensors located on the front and rear secondary shaft of the transfer case) a signal is received from the switching unit to turn on the servomotor, and the clutch is pressed. Thus, torque is transmitted to the front output shaft of the transfer case. When a signal corresponding to the rotation of the wheels on the front and rear axles enters the switching unit, it is sent from there to the servomotor, and the clutch is disconnected. The box returns to two-wheel drive mode again.
Also, the NVG 226 transfer case has a neutral position mode. When this mode is selected, the gearbox and transfer case are excluded from the kinematic diagram when towing a vehicle, which prevents unnecessary load application to these units.
Automatic all-wheel drive system (A4WD)
This system is used in the NVG 126 transfer case. The system works similarly to the corresponding system in the NVG 226 gearbox. The difference is that in the NVG 126 gearbox the automatic all-wheel drive mode is constantly on and is the only one possible.