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Grand Cherokee - Jeep Autopsy

Posted in Features on March 2, 2007 Comment (0)
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Grand Cherokee - Jeep Autopsy
Photographers: Courtesy of Jeep
<strong>The Fact:</strong><br />The Grand Cherokee represented more than $1 billion in plant and product investment. The Fact:
The Grand Cherokee represented more than $1 billion in plant and product investment.

ZJ, WJ, and WK
It's the vehicle that launched "the second 50 years" of Jeep. The Grand Cherokee was an all-new Jeep born out of Chrysler's paint-still-drying Jefferson North Assembly Plant, located in Detroit. But blah, blah, blah. What people really cared about was that 1993 marked the debut of the Grand Cherokee, a cush and capable 4x4 (did we mention cush and capable?) that had a non-argumentative fan base for its entire life-or at least until it went independent "soccer mom" suspension in 2005.

The History
Engineers at American Motors were hard at development on the ZJ as early as 1985, but the company had a tough decision come 1987: build a minivan or an SUV? Even those of you with subpar to zero math skills can figure out which design won. On the bright side, an extra 18 months went into creating the ZJ, which Jeep says became its flagship (we all pretty much know is usually defined as being "priciest" or "leatheriest").

The Concept I was the first introduction to the future ZJ. The Concept I was the first introduction to the future ZJ.

The Model/The Body
One of the few vehicles ever in the history of mankind to actually resemble its concept predecessor, the five-seater ZJ came out in the spring of 1992 as a '93 model and had unibody construction like the baby Cherokee, but was about 10 inches longer and 4 inches wider than the XJ. It was a hit-and all because of having a driver-side airbag and four-wheel ABS! It was also the first Jeep to stuff in a split-bench rear seat.

The ZJ arrived in three levels: base (later called SE), Laredo, and Limited. In 1993 the short-timer Grand Wagoneer got wood, which was top of the line and standard with a V-8. The outdoorsy Orvis came in 1995 (and went in 1998), and as gross as the name sounds, so was its two-tone interior. In 1998 a sportier TSi model was added.

A massive redesign happened for the '99 model year (all but 127 ZJ parts remained), which is when the Grand Cherokee got rounder, a little longer (106-plus inches, but the wheelbase was unchanged), and nabbed its second-gen WJ designation. Laredo and Limited were retained, the headliner Overland was added in 2002, and SE and Sport came and went. For 2004, Special, Freedom, Columbia, and Rocky Mountain Editions busied the lineup.

When the '05 remodel of the Grand happened, morphing into the WK, the Laredo, Limited, and Overland yet again made the rounds. Now featuring a 109.5-inch wheelbase and an overall length of 186.6 inches, it was often criticized for looking a tad like a minivan, which was a polite way of calling it ugly. The high-performance Grands over the years were the '98 5.9 Limited and the street-made SRT8, which hit in 2006. To fest itself that same year, Jeep created a 65th Anniversary Edition Grand that used the Laredo E-package as its muse.

The Worthless Fact:
The idea for the rear suspension on the '93 Grand was scribbled on a cafeteria napkin.

The Engine
The 190hp 4.0L six-cylinder was the standard engine when the ZJ debuted, but later a 220-pony/280 lb-ft of torque 318ci 5.2L V-8 was introduced (and with a notable 6,500-pound tow rating for that class, toppling the six-cylinder's heavy-duty tow package of 5,000 pounds); it was standard in the Grand Wagoneer ZJ. In 1994 any of the ZJs could get the V-8 as an option-as long as it was hooked to an automatic transmission. The following year, the V-8's torque got a minor bump (from 285 to 300 lb-ft), and soon after, the 4.0L's horsepower got a minor drop (to 185) but a blink-and-you-miss increase in torque. The '98-only 5.9 Limited got its name from its 360ci 5.9L V-8, which made 245 hp and 345 lb-ft of torque.

With the WJ in 1999 came a new 230hp 284ci 4.7L V-8 worth 295 lb-ft of torque, while the 4.0L returned with 195 hp and 230 lb-ft of torque. During the '02 model year, the 4.7L became the new-and-improved 287ci 4.7L High-Output V-8 that made 260 hp, standard on the Overland and an option on the Limited. By 2004 the High-Output 4.7L was rated at 265 hp and 330 lb-ft of torque, while the PowerTech version was 235 hp and 295 lb-ft of torque. The High-Output 4.7L was for Laredo and Limiteds.

The '05 model year was the next big thing for the Grand, with the 4.0L dumped in favor of a new 210hp 226ci 3.7L PowerTech V-6 that made 235 lb-ft or torque and featured 9.6:1 compression ratio and was standard on Laredos. The 287ci 4.7L PowerTech V-8 made 230 hp and 290 lb-ft of torque with 9.0:1 compression and was standard on the Limited, and a new 5.7L Hemi V-8, cranking out 325 hp and 370 lb-ft of torque with 9.6:1 compression, was optional on the Limited 4x4. The middle-of-the-pack 4.7L V-8 returned, but with 230 hp and 290 lb-ft of torque. By the '06 model year, its horsepower was 235 and the torque up to 305 lb-ft. The Hemi also saw a little improvement-330 hp and 375 lb-ft of torque.

Introduced in 2006 was the SRT8, which got a tasty 6.1L Hemi that made 415 hp and 410 lb-ft of torque and had 10.3:1 compression, but that's about the only upside to the street-bred Jeep. By 2006 the numbers had increased to 432 hp and 420 lb-ft of torque. And for 2007 the hot word was "diesel," as in a 3.0L common-rail variety made by Mercedes-Benz and that put out 215 hp and 376 lb-ft of torque. The same year, the Grand's 4.7L became capable of running on the other alternative fuel, ethanol (E85).

The Transmission
There are a few freaks out there, but this time we don't mean you. We're talking about manual ZJs. During the '93, '94, and '95 model years, there was a smattering of the standard full-synchro Aisin-Seiki AX15 five-speeds hooked to the 4.0L in the base and Laredo models. The more common sighting was the four-speed automatic with Overdrive (42RE), standard on the Limited, but a pretty commonly picked option on the other two. For the '99 model year, the automatic transmission became the four-speed 45RFE, and for the '01 model year, the 545RFE automatic was new for the 4.7L and given a second Overdrive ratio, intended for better fuel economy and less engine noise. For 2005's redesign, the WK used five-speeds across the board: the W5A580 five-speed automatic with Overdrive was partnered with the V-6, while the V-8s had the 545RFE automatic, again utilizing the dual-gear design.

The Transfer Case
The ZJ had the Command-Trac (NP231) part-time system as standard equipment on the base and Laredo, while two full-time systems were optional for them: Quadra-Trac (NP249) and permanent-full-time Selec-Trac (NP242). The standard T-case for the Limited and Grand Wagoneer was the NP249. Two-wheel-drives hit the market in January 1993, while the Limited went with a two-by choice in 1995. That same year, Jeep eliminated Command-Trac.

Meanwhile, the WJ collected the full-time Quadra-Trac II system, although Selec-Trac moved beyond the six-cylinder and became available in the '00 model year with the 4.7L. In 2002 the Overland could be bought as a two-wheel drive. And come 2005, the now-WK had a full-time single-speed T-case (the Quadra-Trac I NV140) mated to the 3.7L. The Quadra-Trac II and the Quadra-Drive II were variations on the NV245 for the V-8s and optional with the 3.6L; Quadra-Drive II utilized electronic limited-slip differentials.

The Suspension/Axles
Hanging from the ZJ was a tuned-up XJ suspension with about an inch-and-a-half more travel. There was a Quadra-Link solid axle frontend (Dana 30) with four locating arms with coils, and the rear pretty much copied that, calling it Quadra-Coil (with a Dana 35). The '96-and-later V-8 Grands got a semi-floating odd-ball Dana 44 rear. Gearing was 3.55s, although 3.73s were optional. The Up Country suspension was available for the base and Laredo and included skidplates, tow hooks, and a 1-inch-higher ride height. Solid axles stayed on for the WJ design, but it all went awry when Jeep caved to independent front suspension in 2005, switching to IFS AAM 790 and AAM 830 axles front and rear, respectively. The V-8s still had 3.73 gears, while the V-6 got 3.07s.

Jeep Autopsy: Grand Cherokee

SPEED READING
’93 GRAND CHEROKEE ENGINE
Wheelbase: 105.9 in. 4.0L inline-six
Overall length: 176.5 in. Displacement: 242 ci
Overall width: 69.3 in. Bore x stroke: 3.88x3.41
Overall height: 64.7 in. Compression ratio: 8.8:1
Curb weight: 3,633 lbs. Horsepower: 190 @ 4,750 rpm
Transmission:
AX-15 five-speed manual
Torque: 225 @ 4,000 rpm
Transfer case:
NP231
Induction: Multi-point EFI

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