Jeep upgrades Grand Cherokee

  • 16-Apr-2009 08:14 EDT
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A 146% improvement in body stiffness and a new air suspension system contribute to more on-road refinement for the Grand Cherokee.

The 2011 Jeep Grand Cherokee looks little different from the current model, but under the familiar-looking sheetmetal lies an entirely new vehicle that shares hardware, not with previous versions of the Grand Cherokee, but with the Mercedes-Benz ML-Class SUV.

The codeveloped unibody exploits a 53% increase in spot welds, a 42% increase in arc welds, and a 38% increase in structural adhesive to produce a 146% improvement in torsional stiffness for improved durability and reduced NVH. Designers shaved 7% from the Grand Cherokee’s aerodynamic drag, trimming its coefficient to 0.37.

The wheelbase is stretched 5.3 in (135 mm) to 114.8 in (2915 mm), contributing to an additional 4 in (102 mm) of rear-seat knee and leg room. Overall length is up 1.8 in (46 mm) and the Grand Cherokee is 3 in (76 mm) wider. The front door openings are larger—1.9 in (48 mm) wider, 2 in (50 mm) taller—and the rear doors swing open wider—78 instead of 67 degrees—for better ingress and egress. Rear cargo volume is increased by 6.8 ft³ (190 L) to 36.3 ft³ (1030 L).

“The platform has a lot of similarities [to the Mercedes ML] in underbody structure and the engine box area,” remarked Chief Engineer Phil Jansen  “We share suspension geometry, but we added 2 inches of travel for additional off-road capability,” he said. In other places such as the suspension cradle, hardware is shared, but tuning is changed through the use of different bushings, for example.

The Grand Cherokee marks the debut of Chrysler’s all-new 280-hp (209-kW), 260 lb·ft (353 N·m), flex-fuel 3.6-L Pentastar V6 engine, which boasts variable valve timing. The company benchmarked competitive Toyota and Honda engines for refinement, and by its account the new Chrysler engine nearly matches the Toyota and tops the Honda by a wide margin, reported Jansen.

The company paid particular attention to the design of the engine’s aluminum block and to its control technologies to ensure its refinement, he said. This engine will replace all current Chrysler V6 engines in all of the company’s vehicles that use them.

The 360-hp (268-kW), 390-lb·ft (529-N·m) 5.7-L Hemi V8 engine is also available and features variable valve timing and cylinder deactivation for maximum efficiency. While the Grand Cherokee has traditionally sold half its volume with a V8 engine, that mixture has recently shifted to only 30% V8s; with the much-improved new V6, the company expects V8s to account for only 20% of 2011 Grand Cherokees, said Jansen.

Of course the Grand Cherokee features improved suspension and all-wheel drive for better off-road performance. The Quadra-Lift air system lifts the suspension 4.5 in (114 mm) from its lowered “park” mode to its maximum “off-road” mode, where it has 11.1 in (282 mm) of ground clearance.  Additionally, the independent rear suspension, new for the Grand Cherokee, has 10.25 in (260 mm) of travel. Daimler provides the automatic transmissions, transfer case, and rear axle, while ZF supplies the front axle.

The Selec-Terrain system lets the driver adjust the parameters of the Grand Cherokee’s powertrain, braking, and suspension systems to suit different conditions, with automatic, sand/mud, sport, snow, and rock settings.

The top-of-the line Quadra Drive II all-wheel-drive system employs a variable torque, two-speed transfer case and an electronic limited-slip rear differential that allows the Grand Cherokee to route all available power to the one tire that has grip, if that is the case, said Jansen.  “Jeep has always been about giving our customers traction,” he said.

Befitting its shared Mercedes heritage, the Grand Cherokee is moving more solidly into the luxury market, with a more opulent interior and most every luxury option available among its upmarket competitors.

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