Actually it does. I also think Bill did a pretty good job of explaining in layman's terms how the software parameters play a part in the Select-Terrain operation.
There are two separate operations explained in the OM and you need to consider how they both work together...
- QDII operation.
- Select-Terrain operation.
Quadra-Drive® II System – If Equipped
The optional Quadra-Drive® II System features two torque transfer couplings. The couplings include an Electronic Limited-Slip Differential (ELSD) rear axle and the Quadra-Trac II® transfer case.
The optional ELSD axle is fully automatic and requires no driver input to operate. Under normal driving conditions, the unit functions as a standard axle, balancing torque evenly between left and right wheels. With a traction difference between left and right wheels, the coupling will sense a speed difference. As one wheel begins to spin faster than the other, torque will automatically transfer from the wheel that has less traction, to the wheel that has traction.
While the transfer case and axle coupling differ in design, their operation is similar. Follow the Quadra-Trac II® transfer case shifting information, preceding this section, for shifting this system.
So on the WK2 QDII you have torque transfer front to rear but you only have side to side torque transfer on the rear axle. This is different from the older QD system that used gerotor couplers in the transfer case and in both Vari-Lok axles. On that system, 100% torque could be applied to any of the 4 wheels.
The WK2 system is relying on traction and stability control software to make up for the lack of a limited slip differential up front.
SELEC-TERRAIN™ — IF EQUIPPED
Selec-Terrain™ combines the capabilities of the vehicle control systems, along with driver input, to provide the best performance for all terrains. Selec-Terrain™ consists of the following positions:
• Snow – Tuning set for additional stability in inclement weather. Use on and off road on loose traction surfaces such as snow. When in Snow mode (depending on certain operating conditions), the transmission may use second gear (rather than first gear) during launches, to minimize wheel slippage. If equipped with air suspension, the level will change to Normal Ride Height (NRH) if the transfer case is in high range. The level will change to Off-Road 1 if the transfer case is in Low range.
• Auto – Fully automatic full time four-wheel drive operation can be used on and off road. Balances traction with seamless steering feel to provide improved handling and acceleration over two-wheel drive vehicles. If equipped with air suspension, the level will change to NRH.
• Sand – Off road calibration for use on low traction surfaces such as sand or wet grass. Driveline is maximized for traction. Some binding may be felt on less forgiving surfaces. The electronic brake controls are set to limit traction control management of throttle and wheel spin. If equipped with air suspension, the level will change to Off-Road 1.
• Mud – Off road calibration for use on low traction surfaces such as mud. Driveline is maximized for traction. Some binding may be felt on less forgiving surfaces. The electronic brake controls are set to limit traction control management of throttle and wheel spin. If equipped with air suspension, the level will change to Off-Road 1.
• Rock – Off-road calibration only available in 4WD Low range. The vehicle is raised (if equipped with Air Suspension) for improved ground clearance. Traction based tuning with improved steer-ability for use on high traction off-road surfaces. Activate the Hill Descent Control for steep downhill control. Use for low speed obstacles such as large rocks, deep ruts, etc. If equipped with air suspension, the vehicle level will change to Off-Road 2. If the Selec-Terrain™ switch is in ROCK mode, and the transfer case is switched from 4WD Low to 4WD High, the Selec-Terrain™ system will return to AUTO.