The Jeep Grand Cherokee (first two generations)
Click here for the 2005 and later Grand Cherokee.
The Jeep Grand Cherokee made its debut with Bob Lutz behind the wheel, driving straight through a glass window into the North American International Auto Show. The Grand Cherokee started production in a brand new plant, Jefferson North, where it remains. The Grand Cherokee, largely designed by AMC before the buyout, started around 1983 as the next-generation Cherokee, which is one reason the two models are similar in size. After 1987’s buyout, the Grand Cherokee had to take second place to the minivan redesign given limited corporate funds (limited largely due to a surfeit of acquisitions).
Offering safety and comfort, with four wheel drive for foul weather peace of mind, the Grand Cherokee was purchased by unusually affluent buyers, and competed with considerably more expensive vehicles for driveway space. Engineers noted that the vehicle’s inherent vibration frequency seemed to leave drivers feeling more refreshed than many "more refined" competitors.
According to Francois J. Castaing, Chrysler Vice President-Vehicle Engineering and General Manager of Jeep/Truck Platform, talking in 1992, "the Grand Cherokee sets a new standard for on-road ride, handling, and comfort in a sport utility vehicle. It moves that standard closer to some of the best sports sedans on the market today. However, loyal Jeep customers and dedicated off-roaders need not worry, Grand Cherokee improves upon the traditional off-road Jeep virtues of toughness, durability, and go-anywhere utility.”
Compared to the Jeep Cherokee, Grand Cherokee was larger, with a 4.5 inch longer wheelbase, eight inches greater length, five inches more rear-seat hip room, three inches more front-seat shoulder room, 7.4 cubic feet more cargo space, and 4-inch wider rear doors.
While the company claimed “the Grand Cherokee still traverses any trail any other Jeep vehicle can,” it also provided the industry’s first SUV airbag; standard four wheel antilock brakes; the only standard SUV rear wiper/washer; the most efficient air conditioner in its class, with R134 regrigerant; and a choice of part time 4WD, full-time 4WD, and the new QuadraTrac AWD system with a center-mounted viscous coupling that, when needed, automatically locks the center differential for maximum torque transfer.
It also had the most powerful engine in its class, a standard 4.0 liter straight-six with 190 horsepower; unibody construction (first in the class); high torsional rigidity that allowed for a softer suspension; a QuadraCoil solid axle, coil spring, multilink front and rear suspension system for lower cost with greater durability, ride, handling, and off-road capability than competitors; and the lowest weight of any vehicle in the class, with the most front and rear shoulder and hip room.
Coded ZJ, the 1993-98 Grand Cherokee came in Base (which later became SE), Laredo, Limited, and Grand Wagoneer form; even the base model had full instrumentation and cloth seats, while the Laredo added power windows and locks, cruise, body cladding, and aluminum wheels. The Limited had colored lower body classing, leather seats, and more options including a trip computer. The Grand Wagoneer name, an odd choice, was used for a special 318-powered Grand Cherokee with false wood body cladding. The 318 was an optional engine for the Grand Cherokee all the way through to 1998; it was replaced by the 4.7 V8.
In 1996, the model was refreshed with minor exterior changes, while the interior gained dual airbags and a better seat fabric. The 4.0 liter engine was retuned to provide more torque and less noise (moving down to 185 hp), notably using a special intake noise reduction system. The Limited gained numerous luxury features and more options. Also, some export models gained a new Aspen option package.
A five speed manual transmission was available in 1993 and 1994. This was followed by an Orvis Edition from 1995 to 1997, essentially a color package and trim package. In 1997 and 1998, a TSi (taken from Eagle’s naming scheme) edition showed up with minor cosmetic changes, 225/70R16 tires on alloy wheels, leather, and powerful stereo. The big guns were reserved for 1998, to sell the Grand Cherokees when people knew a new version was imminent; the Chrysler 360 V8 engine was installed under the hood and every option they could think of was added; it was called the 5.9 Limited in the US and Limited LX elsewhere. The 360 provided 245 horsepower and 345 poound-feet of torque for a 0-60 time of about 7 seconds, making it the world’s fastest SUV for 1998.
1999 - 2004 Jeep Grand Cherokee
The first Grand Cherokee was redesigned in 1999, for lower production cost and greater performance and reliability; it was Chrysler’s first use of an electronic bus to replace individual wires throughout the body.
From its new V-8, Chrysler's first in three decades, to its five-speed automatic transmission, this was a Jeep with market-leading technology.
The 1999 Grand Cherokee was officially introduced June 16. According to an article on the introduction, Chrysler earned $8,000 from current GC sold. At the time of introduction, the 1998 Grand Cherokee was the second best selling SUV and the best selling SUV you'd actually want to take off road.
Developed in 28 months for $2.6 billion, the 1999 Grand Cherokee was all new, with only 127 carry-over parts (mostly fasteners). It looks similar to the 1998 model, but with sleeker, softer shapes. Chrysler moved the spare tire under the rear floorboard to create more storage space and increased front seat room without forcing drivers with flat tires to get under the car.
1999 Grand Cherokee drivetrain
An all-new 4.7-liter V-8 has slightly more power, less weight, increased fuel efficiency, and lower emissions than the current 318 (5.2). For markets outside the US, there is a 3.1-liter, five-cylinder turbo-diesel with more power and torque than the 2.5-liter Diesel.
4.0 liter six cylinder engine
The 4.0-liter AMC six-cylinder was refined but is still fairly noisy. Power output is 195 bhp/145 kW when meeting Tier 1 U.S. emission standards -- which apply in most U.S. states -- or the European Stage II emission standards. That compares with ratings of 185 bhp/138 kW for the previous-generation engine. Even when complying with California's LEV (Low Emission Vehicle) standards, which reduce emissions about 30 percent from Tier 1 levels, peak output gained five horsepower (3.75 kW) to 190 bhp (142 kW).
The engine has a cast iron block and head with two valves per cylinder. The bore of 3.88 inches (98.4 mm) and stroke of 3.41 inches (86.7 mm) give it a displacement of 3958 cm3 (242 cu in.). A new slitter-vane water pump is 50 percent more efficient than its predecessor, contributing two horsepower (1.5 kW) to the power gain.
A new elastomer-coated steel intake manifold gasket, a two-piece high silicon-molybdenum alloy cast-iron exhaust manifold and a new multi-layer steel exhaust gasket double the expected life over the previous components.
Separation of the exhaust manifold into two pieces reduces internal stress, contributing to the extended life. An automated belt tensioner and coil-on-plug ignition, which eliminates spark plug wires, improve the durability and serviceability of the engine.
The new intake and exhaust manifolds enhance the sound quality of the engine and produce a lower, "throaty" sound preferred by customers. Considerable fine-tuning, including a new laminated oil pan, make the engine 5dB quieter.
Jeep five-speed automatic transmission
An all-new, electronically-controlled transmission with five forward ratios including an alternate second gear ratio for improved performance for passing and better fuel economy is available with the V-8 only, and was designed specifically for Jeeps.
The transmission features unique characteristics such as a tall, 3.00:1 first gear that gives the driver better initial acceleration. Real-time driver adaptive shifting fine-tunes the shift pattern to the driver, while an alternate second gear ratio gives the driver five forward ratios. During acceleration, second gear has a ratio of 1.67. Depending on speed and throttle position, both this gear and an alternate 1.50 second gear ratio are available for kick-down operation, making the down-shift smoother. Its reverse gear ratio is equal to the first gear ratio, to allow for heavier loads.
Other features include three planetary gear sets that combine the widest range of gear ratios available in any transmission in its class. Combined with precise step selections, this brings smooth shifts and maximum power and optimal fuel economy.
The transmission is built at the Indiana Transmission Plant in Kokomo, Indiana, in an all-new 1.2-million square-foot (110,000 m2) facility.
Quadra-Trac II
A new four-wheel drive system, the Quadra-Trac II, incorporates a progressive, speed-sensing torque transfer differential. The system also marks the first industry use of Vari-Lok axles that have a progressive, speed-sensing torque transfer differential in both the front and rear axle. Without any driver involvement, the Quadra-Drive system keeps the vehicle moving even if only one wheel has minimal traction. Unlike other systems, Quadra-Drive works without straining, wearing or compromising the anti-lock braking system.
Quadra-Drive is standard with the V-8 and an option on the six-cylinder. On vehicles assembled in Austria, Quadra-Drive will be offered with all engines.
Under normal driving conditions, the Quadra-Trac II transfer case transfers most of the power and torque to the rear wheels. The moment a wheel loses traction, a speed variation between the front and rear axle occurs and a gerotor pump applies hydraulic pressure to a multi-disc clutch pack. This bridges the coupling, minimizes speed difference and sends power to the front axle.
The gerotor pump is similar to an engine oil pump. The rotor is driven by the front drive shaft and the case by the rear drive shaft which creates a pressurized oil flow to the clutch pack in proportion to their speed variation. As with the pump, clutch discs are alternately splined to the front and rear drive shafts.
Faster response compared to viscous couplings results from the ability of Quadra-Trac II to immediately pressurize the clutch pack and bridge the coupling when a speed difference occurs. A viscous coupling tends to respond more slowly because it indirectly transfers torque through a viscous fluid and never fully bridges the coupling. Another advantage over viscous couplings is that the gerotor pump uses the same lubricant supply as the rest of the transfer case, not needing the extensive sealing between the viscous fluid and the gear lubricant.
As in all Jeep vehicles, the Quadra-Trac II transfer case includes a low range for off-highway operation. Selecting low range gives a torque multiplication ratio of 2.72 and fully locks the center differential.
The gerotor pump incorporated in a Vari-Lok differential is conceptually the same as that used in the Quadra-Trac II transfer case. Its operation is virtually transparent to the driver.
Power transfer in a Vari-Lok differential is proportional to wheel speed difference rather than torque difference as is typically the case in mechanical limited-slip systems. Because conventional limited-slip differentials are initially pre-loaded to assure torque transfer, normal use tends to cause wear that reduces the ability of the differential to transfer torque over time. By design, the Vari-Lok differential is virtually wear free.
Compared to systems with a viscous coupling, which also sense speed, Vari-Lok differentials respond more quickly and smoothly to wheel slip. Response of the gerotor pump can be precisely tuned to driving conditions, enabling the use of this advanced system in the front axle as well as the rear.
All new rear suspension, revised front suspension
The 1999 Grand Cherokee has a new three-link rear suspension with lower unsprung weight and a higher roll center, and a revised front suspension and steering gear. The new tubular front and rear control arms are hydro-formed, making them five times stiffer than the previous design. Modified coil springs are used for all four wheels while standard sixteen-inch wheels and larger tires contribute to a more comfortable ride and better handling.
Solid axles were chosen to provide constant ground clearance for off-highway use, and constant camber that results in better traction both on-road and off-highway.
The new rear suspension is said to let the vehicle corner flatter, while wider spacing of the tie-rod points gives smooth low-speed turns, crisper turn-in response, improved on-center steering feel and reduced tire wear. Changing the track bar geometry resulted in less lateral motion, dramatically improving passenger comfort by reducing head movement on bad roads.
Steering, brakes, and more
An all-new steering gear, with repositioned linkage for better steering feel and response throughout all speed-ranges, improves on-center feel.
The new, integrated anti-lock braking system with electronic brake distribution (EBD) is lighter and less complex than previous systems while providing quieter operation, less pedal pulsation, reduced fade and improved front/rear balance. The 1999 Jeep Grand Cherokee meets or exceeds all U.S. FMVSS passenger car requirements, which are significantly more stringent than those for light trucks.
The brake system anti-lock disc brakes on all four wheels with electronic brake distribution, dramatically improving brake stability. Together with the largest brake rotors in its segment, providing a 22 percent increased swept area.
The UniBody structure is both stiffer and lighter than the body-on-frame construction used by most competitors. Benefits include reduced noise, vibration and harshness, better ride and handling on-road and a smoother off-highway ride.
Both front and rear suspension systems are designed to provide 8.3 inches (210 mm) of travel during articulation. While traversing bumps, the solid front and rear axles maintain their class-leading ground clearance of 9.3 inches (237 mm) and 8.3 inches (210 mm), respectively.
As with every Jeep vehicle, the 1999 Grand Cherokee is designed to be able to cross standing water up to 19 inches (480 mm) deep.
An optional Up-Country suspension package, available on both Laredo and Limited, increases ground clearance by one inch (25 mm).
Jeep Grand Cherokee production
The 1999 Jeep Grand Cherokee is produced at the Jefferson North Assembly Plant in Detroit, with export models being produced in Graz, Austria, and in South America.
