DETROIT -- When Jeep began in 2010 to design a replacement for the Liberty, it faced a fundamental problem: The mid-sized SUV segment, once dominated by Jeep, had moved on.
A segment once full of transfer cases and locking axles was now overrun by vehicles for which "off-road" meant gravel shoulders, not rock climbing. Sales of the Liberty were a fraction of those of rival vehicles from Honda, Toyota and Ford.
Enter the 2014 Jeep Cherokee, Chrysler Group's latest and most complex attempt to graft Jeep's off-road heritage onto the comfort, fuel efficiency and safety of a modern crossover.
With the help of key suppliers -- ZF Friedrichshafen and American Axle & Manufacturing -- that developed two major innovations, the Cherokee is Jeep's best hope to compete with today's Honda CR-V, Toyota RAV4 and Ford Escape.
Among the innovations that make the Cherokee stand out:
• Optional on-demand all-wheel drive and four-wheel drive. Power to the rear wheels is disconnected automatically when not needed, boosting mileage.
• A nine-speed transmission from ZF. Front-wheel drive and extra gears also save fuel.
• A low or crawl gear for off-roading.
Moreover, when production starts next month, all Cherokees will be equipped with either a 2.4-liter I-4 or a 3.2-liter V-6. Both are re-engineered versions of current Chrysler engines.
That means that everything that powers the Cherokee is new -- designed, adjusted and balanced by Chrysler and supplier engineers in just over two years, a daunting and complex task.
"What we needed to do with the replacement for Liberty was not just catch-up," Jeep brand chief Mike Manley said. Mating fuel economy with off-road ability "requires the latest technology, so that means we had to bring them together for the Cherokee," he said.
Whether the Jeep faithful will agree remains to be seen. Reactions to the Cherokee's unorthodox curvy design have been both critical and enthusiastic, but its official reveal was one of the most crowded events at last month's New York auto show.
Simultaneous development
Chrysler Group CEO Sergio Marchionne said last week in Italy that reworking the Liberty platform for the Cherokee was not an option.
He said the Liberty was at least 400 pounds too heavy and engineers couldn't find a way to improve the previous model without starting from scratch.
But Chrysler added to the difficulty of the project by equipping the Cherokee with new engines and a new transmission, plus the new awd and 4wd system, in its first year of production.
Nowadays, many automakers introduce one component, such as a new engine, and then wait a year before adding a new transmission. That method reduces variables and quality errors.
Chrysler engineers worked out the kinks with the help of increasingly sophisticated computer testing, said Mircea Gradu, Chrysler's vice president for powertrain, transmission and driveline engineering. "You can cover a whole variety of operating conditions without trying to do it randomly," he said.
As a result, traditional development time was cut by a third to two years.
Innovative driveline
The Trailhawk version of the 2014 Jeep Cherokee was specially designed for off-roading. It has a low gear for crawling over rocks and a locking differential for added traction. Its crawl ratio 56:1 is a higher, more desirable ratio than that of any other Jeep except the Wrangler Rubicon.
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American Axle & Manufacturing helped develop the key drivetrain parts, which Jeep calls Active Drive, that allow the fwd Cherokee to go awd or 4wd either automatically or at the driver's command.
A unit called a power takeoff connects the driveshaft to the transverse-mounted transmission and sends power to the rear differential. The differential, or rear drive unit, takes the spinning driveshaft and splits the torque to the two rear wheels.
The design is similar to traditional awd systems except for a few key elements: a lower gear and clutches that engage and disengage the rear driveshaft and the differential as needed for traction.
The Cherokee will come with four powertrain options:
1. Fwd on the base model.
2. Optional awd similar to most crossovers.
3. Optional 4wd that engages a low, crawling gear.
4. Optional 4wd with locking differential for added traction.
All Active Drive systems have a neutral position to allow the vehicle to be towed.
For drivers, the single-speed awd system engages automatically or can be set via a switch in the cabin to stay on full time.
Buttons in the cabin also engage the Active Drive 4wd system, its low gear and the locking axle.
Meanwhile, Chrysler engineers adapted an innovative nine-speed transmission from ZF for the Cherokee.
ZF's design uses four gear sets and six shifting elements to improve fuel efficiency by 10 to 16 percent over early six-speed, fwd transmissions.
Chrysler engineers spent months refining the software to meet the Cherokee's on- and off-road demands.
"This vehicle is supposed to be extremely capable and durable, so we put it through its paces in various locations," Gradu said.
ZF also is supplying a nine-speed transmission to the Range Rover Evoque.
New engines, too
The Cherokee's two engines are another example of how Chrysler engineers designed the Cherokee for two uses, the road and the trail.
The standard 2.4-liter I-4 offers greater fuel efficiency but 87 hp less than the optional 3.2-liter V-6. The engines haven't completed EPA testing yet, but sources suggest that the Cherokee's carlike 2wd trim level, outfitted with the smaller engine should achieve mpg ratings of 23 city/31 hwy.
The V-6 will generate 239 pounds-feet of torque and is expected to achieve estimated mpg ratings of 22 city/29 highway.
Production of the 2014 Cherokee -- which debuted at the New York auto show last month -- officially begins May 23, but engineers are still doing last-minute tweaks and testing.
For Jeep, the stakes are high. Manley said the brand needs a strong Cherokee launch to meet its sales goals this year. Jeep had record global sales in 2012 of more than 701,000 vehicles but has been down this year in large part because the Liberty ceased production in August.
"Obviously, I'm expecting some really big things from Cherokee," Manley said. "I don't like being down in the bottom of any league."
Juggling act
Input from key supporters and virtual testing helped Chrysler engineers develop the 2014 Jeep Cherokee in 2 years with
• 2 reworked engines
• A new 9-speed transmission
• Optional awd and 4wd
