The new Selec-Trac II four-wheel-drive system is standard on all Jeep Cherokee models. The Selec-Trac II four-wheel-drive system is a full-time, active on-demand system that anticipates and prevents wheel slip before it occurs. It is ideal for a wide range of road settings, including dry pavement conditions not typically suited for conventional part-time four-wheel-drive systems.
This premium system offers a 4WD Auto mode that is just right for on-road driving. When driving in 4WD Auto mode, the system uses vehicle sensors to adjust and redirect torque between the front and rear axles based upon real-time driving conditions, providing the vehicle with responsive tractive performance.
For added capability when traversing steep grades, rough terrain or extremely poor traction surfaces, the transfer case includes a 4WD Low mode. This second speed gear multiplies engine torque 2.72 times and locks the clutch pack for maximum traction.
The electronically controlled wet clutch pack uses an electric motor to actuate a sector plate. The sector plate then actuates a clutch lever that applies normal force to the multi-disc wet clutch pack. The clutch discs are alternately splined to the front and rear driveshafts. When normal force is applied to this clutch pack, torque is transferred to equalize speed differences between front and rear axles.
Transfer of torque from one wheel to the other on an axle is accomplished by using Brake Traction Control. Under the right conditions the vehicle can be driven by just one wheel.
Electric shifting between 2WD, 4WD Auto and 4WD Low is accomplished with a console-mounted switch. A pushpin button is used to shift to Neutral mode.
Jeep-engineered Hill Descent Control
The same Jeep-engineered Hill Descent Control system introduced on the new Jeep Grand Cherokee in early 2008 is now available on the all-new Cherokee (with an automatic gearbox only). The system was designed to mimic the downhill control and flexibility afforded by the ultra-low gearing found in a Jeep Wrangler Rubicon with its 4:1 ratio transfer case and six-speed manual transmission. This gearing provides for six speeds of controlled hill descent.
Operational in the 4WD Low position, Hill Descent Control provides downhill assistance at a controlled rate of speed with more precision and smoother operation than simply using the brakes. By means of electronic brake control, Hill Descent Control supplements the gear reduction and engine braking that a traditional mechanical low-range transfer case provides. The new Jeep Cherokee with Hill Descent Control offers extremely smooth transitions between speeds and allows the driver to use the throttle and brakes without turning the system off, with a smooth and controlled return to the preset speed after the driver releases the throttle or brakes.
Hill Descent Control is activated with a push of a button in the centre stack. For ease of operation, after the Hill Descent Control button is engaged, Cherokee’s Hill Descent Control is activated and deactivated automatically, as the system senses changes in topography. The system works whether the vehicle is driven in forward or reverse and preset speeds can be selected by using the transmission shifter.
The preset maximum speeds are:
1st gear: 1.6 km/h
2nd gear: 4 km/h
3rd gear: 6 km/h
4th gear: 9 km/h
5th gear or D: 12 km/h
Reverse (R): 1.6 km/h
Neutral (N): 4 km/h
The system is active in all gears.
Once the conditions for activating Hill Descent Control are met the HDC lamp in the instrument cluster will illuminate, indicating that HDC is operating. The system determines when the vehicle is on a slope or level terrain by input from the sensor cluster.
As the vehicle crests a hill, the brakes will automatically adjust the brake pressure to maintain the vehicle at the driver requested set speed - based upon transmission lever position. The vehicle speed can be adjusted up or down by the driver by shifting the transmission between the available gears. Lower gears are slower speeds, higher gears are higher speeds. In addition, the vehicle speed can be reduced by applying the brake, or raised by applying the accelerator pedal to provide a controlled descent down a hill. Once the driver releases the brake or the throttle, vehicle speed will ramp up or down to the pre-determined Hill Descent Control (HDC) limit speed, according to the transmission lever position. Should a driver decide to back down a hill, HDC will limit speed to 1.6km/h, and the driver can modulate this speed by using the brake pedal and accelerator pedal.
Hill Descent Control was engineered to provide the smoothest transitions possible, even from a complete stop on extremely steep and slippery surfaces.
Hill Descent Control is standard on all Jeep Cherokee models with automatic transmissions.
Hill Start Assist
A Hill Start Assist system is new for Jeep Cherokee. It provides the driver time to transition from brake to throttle to achieve a smooth launch on a slope. The system will hold brake pressure for two seconds upon the driver’s release of the brake pedal. The Hill Start Assist system decreases wheel pressure in response to increasing throttle to provide a smooth launch. This system is extremely helpful when driving in urban as well as off-road areas with steep hills.
Hill Start Assist is standard on all Jeep Cherokee models.Published 5 August 2008