Jeep Grand Cherokee

The Jeep Grand Cherokee is a range of mid-size SUVs produced by the American manufacturer Jeep. At its introduction, while most SUVs were still manufactured with body-on-frame construction, the Grand Cherokee has used a unibody chassis from the start.

Development

The Grand Cherokee's origins date back to 1983 when American Motors Corporation (AMC) was designing a successor to the smaller Jeep Cherokee (XJ). Three outside (non-AMC) designers— Larry Shinoda, Alain Clenet, and Giorgetto Giugiaro—were also under contract with AMC to create and build a clay model of the Cherokee XJ replacement, then known as the "XJC" project. However, the basic design for the Cherokee's replacement was well under way by AMC's in-house designers and the 1989 Jeep Concept 1 show car foretold the basic design.

As AMC began development of the next Jeep in 1985, management created a business process that is now known as product lifecycle management (PLM). According to François Castaing, Vice President for Product Engineering and Development, the smallest U.S. automaker was looking for a way to speed up its product development process to compete better against its larger competitors. The XJC's development was aided by computer-aided design (CAD) software systems making the engineers more productive. Meanwhile, new communication systems allowed potential conflicts to be resolved faster, thus reducing costly engineering changes, because all drawings and documents were in a central database. The system was so effective that after Chrysler purchased AMC in 1987, it expanded the system throughout its enterprise, thus connecting everyone involved in designing and building products.

The Grand Cherokee thus became the first Chrysler-badged Jeep product. Development work for the new Jeep model continued and Chrysler's employees (after the 1987 buyout of AMC) were eager for a late-1980s release date; however, CEO Lee Iacocca was pushing for redesigned Chrysler minivans, thus delaying the Grand Cherokee's release until late 1992 as an Explorer competitor. Unlike the Explorer, the Grand Cherokee utilized monocoque (unibody) construction, whereas the Explorer was a derivative of the Ranger pickup with a separate body-on-frame. A Dodge branded version was designed as a precaution should Jeep dealers struggle handling so many Grand Cherokee units.

The Grand Cherokee debuted in grand fashion at the 1992 North American International Auto Show in Detroit, Michigan. The vehicle that was driven was a Poppy Red Clear Coat 1993 Grand Cherokee ZJ Laredo with a quartz cloth interior and high-back bucket seats. Then Chrysler president Robert Lutz drove Detroit mayor, Coleman Young, from the Jefferson North Assembly Plant on North Jefferson Avenue via a police escort to Cobo Hall, up the steps of Cobo Hall and through a plate glass window to show off the new vehicle. Sales of the 1993 model year Grand Cherokee began in April 1992.

Production of the Grand Cherokee started shortly afterward in the purpose-built Jefferson North Assembly in Detroit, Michigan. European Grand Cherokees are manufactured in Austria by Magna Steyr. The Grand Cherokee "played a significant part in reviving Chrysler's fortunes by moving it into the then nascent market for high-margin sports utility vehicles."

Upon its introduction, it was the first full-scale manufacture of an automobile in the US using HFC-134a refrigerant in place of HCFC-12 for the HVAC system.

First generation (ZJ; 1993)

The original Grand Cherokee was launched in 1992 as a 1993 model year vehicle in the luxury SUV segment. The "ZJ" models, manufactured from 1992 to 1998, originally came in three trim levels: base (also known as SE), Laredo, and Limited, subsequent trims were added, included Orvis (MY 95–98), TSI (MY97–98). The base model included features such as full instrumentation, cloth interior, and a standard five-speed manual transmission, while gaining the moniker "SE" name for the 1994 model year. Power windows and locks were not standard equipment on the base trim. The minimal price tag differential resulted in low consumer demand, and as a result, the low-line model was eventually discontinued. Additional standard features included a driver-side airbag and four-wheel anti-lock braking system (ABS). The Laredo was the mid-scale model with standard features that included power windows, power door locks, cruise control, and a leather-wrapped steering wheel. Exterior features included medium-grey plastic paneling on the lower body and five-spoke alloy wheels. The Limited was the premium model, featuring body-color lower body paneling, and gold exterior accents. The Limited also boasted standard features such as leather seating, heated mirrors, front power seats, a keyless entry system, woodgrain interior appliqué, lace style alloy wheels, a driver information center with a compass, digitized climate control, an electrochromic rearview mirror, and Jensen brand stereo with multi-band equalizer. By 1996 the options list grew to include heated seats. Standard was the 4.0, with the 5.2 V8 (and 5.9 in 1998) being optional, as with other models. Package groups with the various trim levels included: fog lamps, skid plates, as well as convenience, lighting, luxury, power, security, and trailer towing packages.

When it was first introduced in April 1992 as an early 1993 model year vehicle, the Grand Cherokee only had one powertrain choice: the 4.0-liter AMC-derived straight-six engine that made . This became the "volume" engine for the Grand Cherokee. Transmission choices included a four-speed automatic transmission (early production ZJs used the AW4—the A500SE (later 42RE) replaced the AW4 during the latter half of the 1993 model year) or an Aisin AX15 manual transmission. Low demand for the manual transmission resulted in its discontinuation after 1994, but European-market ZJs retained it when coupled to the diesel engine (which was unavailable in North America). The drive train choices included rear-wheel drive or four-wheel-drive. In 1995, the engine dropped to due to new EPA regulations imposed on the 1996 model year.

In 1997, for the 1998 model year, a variant of the top-level Grand Cherokee Limited, the "5.9 Limited" was introduced. Jeep ads claimed it to be the "world's fastest sport utility vehicle", verified by third-party testing. The primary improvements in the 5.9 Limited version included a 5.9-liter OHV V8 engine, heavy-duty 46RE automatic transmission, functional heat-extracting hood louvers, unique wide-slot body-colored grille with mesh inserts, special rocker moldings, low-restriction exhaust with three-inch chrome tip, a low-profile roof rack, and special 16" Ultra-Star wheels. The 5.9 Limited also received a 150 amp alternator and a 2-speed electric cooling fan. Other features include a standard 180-watt, 10-speaker Infinity Gold sound system with rear roof-mounted soundbar, standard sunroof, and an interior swaddled with unique "calf's nap" soft leather and faux wood trim. The 5.9 Limited was awarded "4×4 of the Year" for 1998 by '' Petersen's 4-Wheel & Off-Road'' magazine. The production of this model was 14,286 units.

Export models produced at the plant in Graz, Austria, were given the vehicle designation of "ZG".

Engines

Production numbers

Second generation (WJ/WG; 1999)

Launched in September 1998, the redesigned WJ 1999 Grand Cherokee shared just 127 parts with its predecessor (mostly fasteners). The European model was coded WG. The spare tire was relocated from the side of the cargo compartment to under the floor. (Like the 1998MY ZJ, the rear tailgate glass opened separately.) The two heavy pushrod V8 engines were replaced by Chrysler's then-new PowerTech. The new V8 engine produced less torque than the old pushrods, but was lighter, offered better fuel economy, and provided similar on-road performance figures (the fuel tank was replaced with one of a capacity). The straight-six engine was also updated. A redesign of the intake manifold added . While other Jeep vehicles used the Mopar 5 × 4.5 bolt circle, this was the first Jeep following the 1987 Chrysler buyout to receive a wider bolt pattern—5 × 5.

A notable feature available in this generation was the automatic four-wheel drive option called '' Quadra-Drive'', which employed the New Venture Gear NV247 transfer case. This two-speed chain-driven transfer case uses a gerotor, a clutch pack coupled to a hydraulic pump, to transfer torque between the front and rear axles. The transfer case contains three modes, 4-All Time, Neutral, and 4-Lo. In 4-All Time, 100% of torque is sent to the rear axle in normal conditions. If the rear axle starts spinning at a higher rate than the front axle, hydraulic pressure builds up in the gerotor and causes the clutch pack to progressively transfer torque to the front axle until both axles return to the same speed. A neutral mode is intended for towing the vehicle. In 4-Lo, the front and rear axles are locked together through a 2.72 reduction gear ratio. The NV247 transfer case is mated to front and rear axles containing Jeep's Vari-Lok differentials. Vari-Lok differentials also use a gerotor to transfer torque between the wheels on either side of the axle. The major advantage of Quadra-Drive was that the combined transfer case and progressive locking differentials in each axle could automatically control traction between all four wheels. However, only the center differential could be permanently locked, and only in 4Lo. The Quadra-Trac II system included the NV247 transfer case with the standard open front and rear differentials.

The '' 45RFE'' and '' 545RFE'' automatic transmission in the WJ was notable. It included three planetary gear sets rather than the two normally used in a four-speed automatic. This gave it six theoretical speeds, and it would have been the first six-speed transmission ever produced in volume, but it was programmed to only use five of these ratios. Four were used for upshifts, with a different second gear for downshifts. Although five of the six ratios were used, Chrysler decided to call it a "4-speed automatic". For MY 2001, the programming was changed to make use of all six ratios. Rather than have six forward gears, the transmission was programmed to act as a five-speed with the alternate second gear for downshifts. The rpm at on a 545RFE is 2,000 rpm, 200 rpm less than the 45RFE programming. 1999 and 2000 model-year WJ owners can have their 45RFE transmission's programming flashed to enable the extra gear as both transmissions are physically the same. (Must purchase new PCM and ABS module and program them with a fake VIN to make this work.) The 42RE 4-speed automatic remained the transmission for the inline 6 engine. It had slight changes from the previous model Grand Cherokee.

The interior was also completely redesigned. The redesign allowed for larger rear doors, and more space for rear passengers. Controls for various items like headlights, heated seats, and rear wiper were moved to more convenient locations. The electronic Vehicle Information center was moved from below the radio to above the windshield and was standard on 2000–2004 models. Limited models included automatic dual-zone climate control. A 10-CD changer was also available with the Infinity Audio package.

In addition to Jeep's UniFrame construction, Daimler Chrysler partnered with Porsche to further strengthen the frame. This was done to reduce Noise Vibration Harshness (NVH). UniFrame is an unusual construction scheme, it incorporates all of the strength and durability of a body-on-frame construction into a unitized construction. By adding stiffness and rigidity to the structure, they enhanced the ride and strengthened the network of steel beams, rails and pillars (or "safety cage") that surround and protect occupants. More than 70 percent of the underbody is high-strength steel. All Jeep Grand Cherokees feature UniFrame construction.

The Grand Cherokee received a minor facelift for 2004 including round fog lamps, a lower front fascia, and a new body color-matched inset grille design.

Export models produced at the plant in Graz, Austria, were given the vehicle designation of "WG".

Engines

Third generation (WK; 2005)

The WK Grand Cherokee debuted in 2004 for the 2005 model year at the 2004 New York International Auto Show with available Quadra-Drive II four-wheel drive, rear-seat DVD player and optional 5.7-liter Hemi V8. The 3.7-liter V6 engine replaced the 4.0-Liter straight-6. A Mercedes-Benz-sourced 3.0-liter V6 Common Rail Diesel (CRD) was available outside of North America from launch.

Jeep replaced the XJ-era leading-arms live-axle front suspension (found in the ZJ and WJ) with an independent double-wishbone setup like that which debuted in the 2002 Liberty. Classed as a truck-based SUV, the WH/WK Grand Cherokee offers "crossover" refinement, capability and NVH.

The 2007 Jeep Grand Cherokee made its European debut at the Euro Camp Jeep in Ardèche

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