Perhaps no other automotive brand has more of a reputation or legacy for off-road driving than Jeep. And when it comes to adventuring into the wild, buyers of the Jeep Grand Cherokee get a choice of three 4-wheel-drive (4WD) systems—Quadra-Trac I, Quadra-Trac II, and Quadra-Drive II—each one designed and geared to take on different levels of capability when departing from the beaten path. Here’s how each system works.
For the everyday driver, Quadra-Trac I is the most straightforward of the three off-road systems. It is a single-speed, full-time all-wheel-drive (AWD) system requiring no direct involvement from the driver to engage. It is always in operation.
Quadra-Trac I is rear-wheel biased, meaning the system sends 48 percent of engine power to the front axle and 52 percent to the rear axle. This front-to-rear ratio remains constant at all times, regardless of the conditions under which the vehicle is driving. Whether it’s dry pavement, wet pavement, or icy pavement, Quadra-Trac I is always on and always slightly favoring the back wheels.
However, the system uses open differentials that channel power between right and left wheels depending on specific needs. The traction control system governs the differentials, which work with the vehicle’s brakes to prevent wheel slippage. If the system senses a wheel is losing grip with the road, it applies the brakes to that wheel, thus giving the other three wheels more engine torque.
Quadra-Trac I has no low-range mode for the driver to choose, like with more sophisticated 4WD systems. Quadra-Trac I is standard on Grand Cherokee Limited and Laredo models at the entry point of the model range.
As the name suggests, the Quadra-Trac II system is the more advanced version of Quadra-Trac I. In some ways, the two systems are alike.
They both feature open differentials and a brake-based traction control system. Also, like Quadra-Trac I, the up-level Quadra-Trac II system has the same rear bias, splitting engine torque 48:52, front to back.
But in this case, the 48:52 split is not a fixed ratio. Instead, Quadra-Trac II utilizes a more sophisticated transfer case with an electronically controlled clutch pack paired with the center differential. This setup enables the system to automatically send up to 100 percent of engine power to either axle at any time, depending on traction needs. The system also utilizes sensors to determine which wheels are slipping and which should receive extra power.
In addition, Quadra-Trac II has a driver-selectable low-range mode for taking on more challenging terrain and weather conditions. This lower gearing gives the vehicle some extra ability and confidence over uneven surfaces in a way that Quadra-Trac I does not allow, but the system still has its limitations. It’s not the ideal setup for extreme off-roading or ice driving.
Quadra-Trac II comes as a standard feature on the mid-level Jeep Grand Cherokee Trailhawk but is optional on other models across the Grand Cherokee lineup.
At the top of the 4WD food chain is Quadra-Drive II. This system gives the Grand Cherokee the off-road prowess for which the Jeep brand has become synonymous. Quadra-Drive II uses the same transfer case as the Quadra-Trac II system, so both setups aptly move power from front to back. But after that, the performance differences and level of sophistication between the two systems become evident.
Quadra-Drive II takes capability up a whole notch by giving each axle its own electronically operated limited-slip differential with a clutch pack. This configuration allows Quadra-Drive II to move up to 100 percent of engine power to a single wheel. When all power goes to either the front or the back, it can then move left or right to whichever corner has the most grip at any given moment.
Due to its ability to freely move power between axles and wheels, the Quadra-Drive II system does not need to use the braking system to combat wheel slip in the way the Quadra-Trac systems do. Instead, this system proactively and predictively reallocates power to compensate for lost traction. Add to this functionality a low-range gearing mode and hill-descent control for true mastery of the ups and downs.
Quadra-Drive II is a standard feature on the top-level Grand Cherokee Summit and is available on the penultimate Overland trim.
Which 4WD system is right for you depends on your off-road intentions. Quadra-Trac I may be the right fit for those planning to do some occasional weekend camping, with most driving occurring around town. Quadra-Trac II could be the better choice for those who crave a bit more adventuring into the wild or live in colder climates with more wintry conditions. And for those who have a yearning to tread the trails of Moab or other extreme environments, Quadra-Drive II is likely the answer.
Sometimes, a 4WD system just needs to be driven to be fully understood. Test drive Quadra-Trac I, Quadra-Trac II, and Quadra-Drive II to experience all three systems’ operational differences and overall feel.