4WD systems that go anywhere
The 2011 Jeep Grand Cherokee offers three 4x4 systems - Quadra-Trac I®, Quadra-Trac II® and Quadra-Drive® II with Electronic Limited-Slip Differential (ELSD).
Quadra-Trac I delivers full-time four-wheel drive without any switches or levers to pull. The system provides smooth operation over a variety of road conditions. This light-weight single-speed case is both proven and highly efficient for enhanced fuel economy.
Quadra-Trac II®s two-speed transfer case uses input from a variety of sensors in order to determine tire slip at the earliest possible moment and take corrective action. The system uses Throttle Anticipate to sense quick movement in the throttle from a stop and maximizes traction before slippage occurs. When tire slippage is detected, as much as 100 percent of available torque is instantly routed to the axle with the most traction.
Quadra-Drive II, with a rear Electronic Limited-Slip Differential (ELSD), delivers industry-leading tractive capability. The system instantly detects tire slip and smoothly distributes engine torque to the tire(s) with traction. In some cases, the vehicle will anticipate low traction and adjust in order to proactively limit or eliminate slip.
(Standard on Laredo 4x4 models)
The ITC (Integrated Transfer Case, MP2010) is a single-speed transfer case and it is used in Grand Cherokee's new Quadra-Trac I Full-Time 4-Wheel Drive System. It provides convenient full-time 4-wheel drive. The transfer case operates with an open center differential dividing engine torque 50 percent torque to the front axle and 50 of torque to the rear axle. The Brake Traction Control System, which combines standard ABS and Traction Control, provides resistance to any wheel that is slipping to allow additional torque transfer to wheels with traction. The MP2010 single-speed transfer case provides the following benefits:
(Standard on SRT8 models)
The MP3010 is a single speed transfer case which provides convenient full-time all-wheel-drive. No driver interaction is required. The DTCM module governs the torque split between the front and rear axle. Driving down a straight line on a dry surface the transfer case sends 47 percent of the torque to the front axle and 53 percent of torque to the rear axle. This four-wheel drive (4WD) system allows front and rear wheels to rotate at different speeds when required by the road condition or road surface.
Normal All-Wheel Drive allows front and rear wheels to rotate at different speeds on all road surfaces. The "SVC 4WD" warning light monitors the electric shift 4WD system. If this light remains on after engine start up or illuminates during driving, it means that the 4WD system is not functioning properly and that service is required.
Proper operation of all-wheel drive vehicles depends on tires of equal size, type and circumference on each wheel. Any difference in tire size can cause damage to the transfer case.
The DTCM (Drive Train Control Module) is an electronic module that controls the shifting of the 4WD "Active on Demand" MP3010 single speed transfer case.
(Standard on Limited and Overland 4x4 models)
The Quadra-TracŪ II is the MP3023 two-speed, on-demand, active four-wheel drive transfer case that provides optimum traction for a wide range of conditions, while maximizing driver convenience. When operating in 4WD Auto mode, this sophisticated system anticipates and prevents slip by redirecting torque as necessary.
For added traction 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.
Electric shifting between 4WD AUTO and 4WD Low is effected with a console-mounted switch. A pushpin button is used to shift to Neutral mode.
The MP3023 transfer case provides the following benefits:
Transfer case operating ranges are:
The 4WD Low range is for off road use only. It is not for use on hard surface roads unless the road surface is wet, slippery, or covered by ice and snow.
The low range reduction gear system is operative in 4WD Low range only. This range is for extra pulling power in off road situations. Low range reduction ratio is 2.72:1.
Controls for the MP3023 transfer case active clutch (torque biasing device) are located in the Drive Train Control Module (DTCM) and communicated on the Controller Area Network (CAN) C bus. The DTCM monitors multiple vehicle sensors to anticipate conditions which may result in wheel slip or reduced performance and preemptively adjusts torque split to front and rear axles as needed. The DTCM also compares wheel speeds at the front and rear axles to detect wheel slippage. A complete vehicle dynamics model, or algorithm, calculates slip at each tire for given vehicle-operating conditions. When wheel slip is detected, pressure applied to the transfer case clutch pack can be increased or decreased to apply increased torque to the axle with higher traction.
Electric Shift Mechanism:
The electronically controlled wet clutch pack uses an electric motor to actuate an internal gear train, clutch cam, and low range barrel cam. The clutch cam actuates the clutch levers that apply normal force to the multi-disc wet clutch pack. The clutch discs are alternately splined to the front and rear drive shafts. 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.
(Optional on 2011 Overland 4x4; Optional on 2012 Limited and Overland; Standard on 2012 Overland Summit and SRT8)
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