2011 Jeep Wrangler
2011 Jeep Wrangler; photo by Peter Bleakney. Click image to enlarge

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By Peter Bleakney

Jeep is synonymous with four-wheel-drive, and the company has come a long way since 1941 when the Willys military vehicle started making tracks. With the 2011 Jeep line-up consisting of five name-plates, there are no less than nine 4×4 systems on offer, seven of which garner the “Trail Rated” badge. This means they pass tough Jeep criteria that include approach, breakover and departure angles, ground clearance, water fording capabilities, axle articulation, manoeuvrability and traction.

Freedom Drive I – Available in the compact Compass and Patriot, this system operates in fuel-efficient front-wheel-drive mode during normal driving, but will send up to 50 per cent of power to the rear wheels via a multi-plate coupling when front wheelspin is detected. It can be locked in 4×4 mode for more demanding conditions. Not Trail Rated.

Freedom Drive II – Again, only on Compass and Patriot (and only with CVT), its 19:1 crawl ratio is coupled with increased ride height, skid plates, front and rear brake differential locks and hill descent control to give these compact utes serious off road ability. Still runs in front-wheel drive when not boonie-bashing. Trail Rated.

2007 Jeep Patriot
2007 Jeep Patriot; photo by Paul Williams. Click image to enlarge

Command-Trac I – Standard on the iconic Wrangler Sport and Sahara, this legendary part-time system has served Jeep owners well through the years although it is not particularly well suited to on-road driving. 2WD High is the usual driving mode wherein the front driveline is disengaged from the transfer case and power goes to the rear wheels. To shift into 4WD, the vehicle must be traveling under 88 km/h, and once engaged, the front and rear drive shafts are locked together; rotating at the same speed. Great for slippery surfaces like snow and dirt but dry pavement can cause binding and wheel hop. The 2.72:1 low range (4Low) must be engaged with the vehicle in neutral and coasting at four to six km/h. It’s all done with a manly shift lever sprouting from the transfer case. Trail Rated.

Rock Trac – Only found on the Wrangler Rubicon, this is the ultimate in off-roading hardware from Jeep. It is a part-time system similar to Command -Trac I – the main difference being its heavy duty transfer case fitted with a 4:1 ratio for more torque and low speed manoeuvrability. There is also a ridiculously low 73.1:1 ratio for crawling over rocks and making custom parking spots at the mall. Rock Trac was developed specifically for the Rubicon, and works in conjunction with other components like Dana 44 axles, Tru-Lok front and rear electronic locking differentials and electronically disconnectable sway bars that allow for a 25 per cent increase in wheel articulation.

2011 Jeep Grand Cherokee
2011 Jeep Grand Cherokee; photo by Jil McIntosh. Click image to enlarge

Command-Trac II – Standard on the mid-sized Liberty SUV, this part-time system differs from Wrangler’s Command-Trac I only in that the balky shift lever is replaced with an electronic console-mounted switch. As with C-T I, there is a neutral position that allows towing without having to uncouple the drive shafts.

Selec-Trac II – Optional, and specific to the Liberty, this Trail Rated system is classified as active full-time 4WD, and is suited to all driving conditions. It is an evolution of the rugged Command Trac II, and here the central transfer case has a clutch pack that predicts conditions that may cause wheel slip and divvies up torque between the front and rear axles based on real-time driving conditions. It is a purely mechanical system. Hill Descent is included, as is 4Low, where the front and rear axles are locked for extreme off-roading. Like Command-Trac, it can also run in 2WD. One third of Canadian Liberty buyers pick Selec-Trac II.

Quadra-Trac I – Standard on the base Grand Cherokee Laredo, this full-time 4WD system is not Trail Rated. Simple in its operation, all four wheels are powered all the time with a default 48/52 front to rear torque split. When there is a difference between front-to-rear axle speed, the system’s brake traction control redirects power the axle with the most grip by braking the slipping wheels. It can distribute up to 100 per cent of torque front to rear.

2011 Jeep Grand Cherokee
2011 Jeep Grand Cherokee; photo by Jil McIntosh. Click image to enlarge

Quadra-Trac II – Expands on the Quadra-Trac I with the addition of 2.72:1 low range and lockable centre differential. Standard on the Grand Cherokee Limited and Overland, Quadra-Trac II is Trail Rated.

Quadra-Drive II – This is Jeep’s most advanced active full-time 4WD system, and is part of the package when you choose the 5.7-litre Hemi engine ($1,900) on the top-trim Grand Cherokee Overland. It uses the Quadra-Trac II transfer case plus electronic limited slip differentials on both front and rear axles enabling the system to transfer torque from side to side. Quadra-Drive II has the ability to send 100 per cent of the engine’s torque to one wheel if that’s the only one with grip.

The 2011 Grand Cherokee has two other off-roading tricks up its sleeve. Jeep Quadra-Lift air suspension (standard on Overland) offers load levelling plus a total of 10.4 cm of ride height adjustment, with five preset levels, ranging from tippy-toe rock crawling to park mode for easy entry/exit.

New Jeep Selec-Terrain, available across the Grand Cherokee line, is similar to Land Rover’s Terrain Response. It has five driver selectable settings (Sport, Snow, Auto, Sand/Mud, Rock) that adjust 12 dynamic parameters of the ute for optimum performance in these conditions.

It all works swimmingly. A 5.7-litre V8 Grand Cherokee armed with all the doohickies carried its weighty and luxurious self over a tough and technical off road course with uncanny ease.

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