All-wheel drive control system and transfer case

There were several all-wheel drive schemes on cars with the GMT800 and GMT900 platforms. Models with permanent all-wheel drive (Full Time), models with a connected front axle (Part Time), and also the system of automatic connection of the front axle (Auto 4WD). Therefore, in the history of the two platforms, various transfer cases from two manufacturers Borg Warner and New Venture Gear were used, depending on the configuration and year of manufacture. Sometimes the manufacturer refers to the Full Time system as AWD (All Weel Drive). A feature of gearboxes for these American cars can be considered that all control is electronic, using switches and actuators. There are practically no classic four-wheel drive control handles.

Platform GMT800

Escalade models have been used for a very short time New Venture Gear model NVG 149 (RPO NP3), which was a single-stage, operating according to the Full Time scheme. The box provided the distribution of torque under normal road conditions between the front and rear axles in a ratio of 32:68. When the wheels of the rear or front axle slip, the center differential, using the viscous coupling of the transfer case, ensures the distribution of torque on «not skidding» axis up to 100% (those. locking of the center differential).

When slipping the front axle

When slipping the rear axle

The most popular transfer case BW 4481 (PRO NR3) Borg Warner provided the scheme for the Full Time all-wheel drive system. The box was also single-stage and provides a torque distribution between the front and rear axles in a ratio of 40:60. It was installed on Cadillac Escalade GMT800 cars from 2003 to 2006 together with the stability control system (VSES). But there is no center differential in the box, and the torque distribution remains constant.



Early production Tahoe GMT800s used a single 261 transfer case (PRO NP2) with switching between 2WD and 4WD modes using the control levers in the cabin. The box had 3 modes 2WD, 4HI and 4LO. But on release models since 2001, it was removed from the configuration.


Since 2001, a New Venture Gear model NVG 263 transfer case was also installed, which provided the Part Time all-wheel drive scheme. The transfer box provides three operating modes: 4Hl, 4LO, 2HI. Switching between modes is also carried out using the switches located on the dashboard.

On cars Tahoe GMT800 2001-2006. release was mainly used transfer case company New Venture Gear model NVG 246 (RPO NP8). Two-speed gearbox with automatic torque distribution system. On the dashboard are switches for controlling the all-wheel drive system. The transfer case provides five modes of operation: Auto 4WD, 4Hl, 4LO, 2HI and N (neutral). Under normal driving conditions, the Auto 4WD mode is used. The control system controls the slippage of the rear wheels, according to the signals from the speed sensors of the front and rear cardan shafts. In the event of slippage of the rear wheels, the system redistributes the moment (increases the speed of the front wheels) to the speed of the rear wheels by means of a clutch. The rest of the modes are classic.






In contrast to the transfer case BW 4481 (PRO NR3), installed on the Escalade model, the BW 4482 transfer case is two-stage and provides a Full Time all-wheel drive system scheme with torque distribution in the same 40:60 range under normal conditions (4HI mode). By means of switches it is possible to select the modes 4HI, 4LO (downshift). There is also a neutral position on the transfer case. Like the BW 4481 box, the 4482 transfer case was installed on vehicles with VSES. The VSES switch is located on the transfer box control panel. During the operation of the VSES system, not only elements of the ABS system are involved (speed sensors, modulator, etc.), but also the transfer case is controlled.

GMT900 platform

On the new platform models, the NVG 246 RPO NP8 transfer case was installed, which was used on the GMT800 platform. Corresponding to the complete interior change in the new models, the four-wheel drive control switches have received a new look.

A Borg Warner transfer case was also installed (BW) model 4485NR3 (single stage, planetary transfer case), providing a torque distribution between the front and rear axles in a ratio of 40:60 (Full Time or All Wheel Drive (AWD)). The new transfer case does not differ much from the BW 4481 used on the GMT800 platform.