Since the 1940s, Jeep has been the most dedicated off-road vehicle brand on the planet. Now that its 75th anniversary has passed, Jeep is still the same Jeep, but the equity has changed. In the current Jeep camp, various products have covered all vehicle categories from small to large, from amateur to professional, and the corresponding four-wheel drive systems are also ever-changing. It is often confusing. For example, there are Active Drive, Freedom Drive, Quadra-Trac, Selec-Tev, Quadra-Drvie, are they completely confused? So, how many four-wheel drive forms does Jeep have? There are ten types in total, and what are the differences between these four-wheel drive systems? Next, we will explain them one by one.
However, a misunderstanding must be explained before the explanation, that is, 4WD does not mean full-time four-wheel drive. The structure of Jeep’s four-wheel drive system also includes full-time four-wheel drive and part-time four-wheel drive. Of course, no matter what kind of four-wheel drive structure is used, the final effect it can bring is to provide stronger grip and tracking on low-adhesion road surfaces.
At present, the full-time four-wheel drive system mostly uses a multi-plate clutch as the central differential. Such a four-wheel drive system usually distributes power to four different wheels under the control of a computer. According to different needs, the four wheels get Torques are not the same. Such a structure is of great help to improve the tracking performance of the vehicle, and it is also helpful to the form safety of the paved road. However, such a system is obviously not suitable for extreme off-road conditions. The part-time four-wheel drive system is mostly matched with the transfer case, and there is no central differential. The connection between the front and rear axles is hard-wired, which can withstand large torque output. But such a system is not suitable for road driving. In Jeep’s product series, according to the positioning of the models, it can be roughly divided into two structural characteristics: full-time four-wheel drive and part-time four-wheel drive, and the mutual integration of these two structural types has also been realized according to different models.
Active Drive System
First of all, Jeep’s Active Drive System is one of Jeep’s entry-level four-wheel drive systems, and it is mainly equipped with two urban SUVs, Cherokee and Renegade. This system detects the front axle through sensors. Once the front axle slips or the rear axle needs power, the system will automatically press the central clutch plate to transmit power to the rear axle. This is its basic operating principle. According to different models, Active Drive System can evolve into several modes such as Active Drive Low, Active Drive I, Active Drive II and Active Drive Lock. Among them, the first mode is to add a low-speed gear switch, which is currently only equipped with the Renegade Trailhawk model, which can achieve a maximum reduction ratio of 20:1.
Active Drive I is currently only equipped on low-end models of the Cherokee, which is the most entry-level configuration, and can only realize power distribution between the front and rear axles. Active Drive II is equipped with models above Cherokee Limited. Compared with Active Drive I, Active Drive II has added a low gear, and the final reduction ratio has increased to 56:1. The system also comes with a neutral mode for trailering. Active Drive Lock is the most advanced configuration in the Active Drive series. It is currently equipped on the Cherokee Trailhawk model. This system is derived from Active Drive II, and an additional rear axle differential lock is added to this technology. At the same time, the off-road locked mode also improves the climbing performance of the vehicle.
Command-Trac 4×4
The Command-Trac system originated in the 1980s and is one of Jeep’s most classic four-wheel drive systems. Its classic feature is that it adopts the most traditional transfer case structure and is not equipped with a central differential lock. The four-wheel drive system can only be used in extreme off-road situations. The transfer case has a maximum torque multiplication factor of 2.72:1 in the low gear. At present, the models equipped with this system are mainly the entry-level models of the Wrangler, such as the Wrangler Sahara and the sports version.
Rock-Trac
The Rock-Trac four-wheel drive system is the standard configuration of the Wrangler Rubicon. This system is based on Command-Trac and is also a part-time four-wheel drive structure. However, it adds an electronic differential lock and has an active front anti-roll bar disconnect function. Under the effect of this system, the climbing ability of Wrangler Rubicon has been comprehensively improved. The matching transfer case is NV241 OR, and the torque amplification ratio of its low gear can reach 4:1. The Rock-Trac four-wheel drive system is currently Jeep’s most powerful four-wheel drive system.
Quadra-Drive II 4×4
The Quadra-Drive II 4×4 system is the standard configuration of the Grand Cherokee Limited, Overland and Summit. It is characterized by the addition of a full-time four-wheel drive option, and a certain degree of improvement in extreme off-road performance. In terms of driving modes, five working modes are provided, including limit, road and off-road, and can be used with air suspension to improve off-road capabilities. The central differential matched with this system is an electronically controlled limited-slip differential, while the axles use open differentials.
Quadra-Trac I 4×4
Quadra-Trac I 4×4 is the entry-level configuration of the Grand Cherokee. Unlike the aforementioned Quadra-Drive II 4×4, this system does not provide any mode selection, and the limited slip between the wheels is also performed by brakes. This system is not suitable for extreme off-road, but only provides a full-time four-wheel drive solution.
Quadra-Trac SRT 4×4
Quadra-Trac SRT 4×4 is equipped with the Grand Cherokee SRT model, and its biggest feature is that it puts more emphasis on handling performance. Equipped with an E-LSD differential at the rear axle, it also allows 100 percent of the torque to go to either wheel. The matched central differential is a wet clutch, and five driving selection modes are also provided in terms of driving mode selection.
Quadra-Trac II 4×4
Quadra-Trac II 4×4 is optional on the Limited, Overland, and Summit models of the Grand Cherokee, and this system is suitable for light off-roading. Unlike the standard Quadra-Drive II, the Quadra-Trac II 4×4 system provides a two-speed transfer case that allows 100 percent of the torque to be transmitted to the front and rear axles. In terms of mode selection, five selection modes are provided, and the maximum torque amplification ratio of the transfer case is 2.72:1. The Quadra-Trac II 4×4 system is currently the most balanced set of solid off-road performance and road performance in the Jeep brand.
Freedom Drive
The Freedom Drive system is currently configured for Jeep guides and free passengers. Like the ActiveDrive system, Freedom Drive can only provide a mild off-road experience. According to different performances, Freedom Drive is also divided into Freedom Drive I and Freedom Drive II. The core of the Freedom Drive system is the matching with the CVT gearbox, while the Active Drive system mentioned above is the matching with the nine-speed automatic transmission. Freedom Drive also transmits the rear axle torque through multiple clutches, while Freedom Drive II adds the locking function of the CVT gearbox on this basis. By locking the size of the active and passive wheels of the CVT gearbox, a certain range of low-speed torque can be achieved Magnification function, but far less than the aforementioned Wrangler in terms of structural strength. And this system is also a product of Jeep’s previous generation, and it shares technology with the technology of the former owner Daimler Group. With the establishment of Fiat Chrysler and the upcoming replacement of Compass, this technology will gradually move from the stage to the backstage.
