The Jeep Grand Cherokee combines mountain-goat agility in rugged terrain with stable and responsive handling on the paved roads where most buyers will spend most of their time.
The Laredo and Limited come standard with Chrysler's 3.7-liter V6, borrowed from its sister trucks, the Jeep Liberty and Dodge Ram, with its own five-speed overdrive automatic transmission. The single overhead cam V6 produces 210 horsepower and gets an EPA-rated 15/20 mpg City/Highway with four-wheel drive and 16/21 with rear-wheel drive, not much better than the V8s. The V6 is capable of towing 3500 pounds, but it's overmatched in the Grand Cherokee, and doesn't provide willing passing power.
The 4.7-liter V8, on the other hand, works really well in the Grand Cherokee. This modern, overhead-cam engine is smooth and powerful for around-town and highway driving. It has a broad torque band, a lovely sound, and electronic throttle control (drive-by-wire) that's easy to use and precise in tricky downhill off-road situations. If you don't live in the mountains, this engine might be your best choice. The 4.7-liter V8 produces 305 horsepower at 5650 rpm and 334 pound-feet of torque at 3950 rpm. It's EPA-rated at 14/19 mpg with rear- or four-wheel drive. It's also flex-fuel capable, meaning it can run on gasoline or up to 85 percent ethanol (E85). And it can tow up to 6500 pounds.
The 5.7-liter Hemi V8 is also a thoroughly modern engine, featuring twin spark plugs, direct ignition, and electronic throttle control, though it is a pushrod-overhead-valve design. The Hemi is upgraded for 2009. It now produces 357 horsepower (up from 330) at 5200 rpm, and torque is up from 375 to 389 pound-feet at 4350 rpm. Fuel economy is an EPA-rated 13/19 mpg with rear drive and 13/18 mpg with four-wheel drive. Note that the Hemi delivers much stronger torque yet matches the fuel economy of the 4.7-liter. Torque is that force that propels you from intersections and helps you tow trailers up long grades, and it can really feel it with the Hemi. With the 2009 changes, the Hemi is stronger than ever, giving the Grand Cherokee head-snapping low-end thrust and power that keeps on pulling.
The Hemi's highway fuel economy rating is aided by Jeep's Multi-Displacement System, which shuts down four of the engine's eight cylinders whenever it detects a steady-state cruise condition and then reactivates them on demand. The Hemi also has a Fuel Saver Mode display that informs drivers when four cylinders have been shut down.
The 4.7- and 5.7-liter V8 engines use a heavy-duty five-speed automatic transmission with a direct fourth gear for towing. Both this transmission and the five-speed automatic that's mated to the V6 feature a manual shift gate.
The 3.0-liter common-rail turbo-diesel (CRD) V6, engineered by Mercedes-Benz, produces 215 horsepower at 3400 rpm and 375 pound-feet of torque at 1600 rpm. That's as much torque as the Hemi, at half the engine speed. Towing capacity also matches the Hemi, at 7400 pounds (with 2WD); while EPA fuel economy of 18/23 mpg with rear-wheel drive (17/22 mpg with four-wheel drive) yields a driving range of more than 400 miles on one tank of fuel. Clean-diesel technology reduces carbon-dioxide emissions by 20 percent, but the diesel is not clean enough to be sold in Maine, New York, Vermont, Connecticut or California.
On the road, the diesel is considerably rougher and noisier than either V8. That's surprising because most modern diesels are smoother. We did observe about 23 mpg in 300 miles of mostly highway driving, though, which is impressive for a midsize SUV.
The Grand Cherokee offers a nicer ride and better cornering than any other Jeep in history. We don't recommend flinging 4500-pound SUVs into corners, but the Grand Cherokee is competent in this sort of socially unacceptable behavior because it's easy to drive and rewarding within the limits of its tires. There seems to be a flatfooted, stable attitude with this Jeep, similar to that of the car-based crossover SUVs recently introduced (in fact, it's better than some). The steering is reasonably quick, accurate, and nicely weighted. A tight, 37.1-foot turning circle provides advantages off-road as well as in crowded parking lots or when making a U-turn. Still, the Grand Cherokee feels more like a truck than the typical crossover SUV.
Three different four-wheel-drive systems come with confusing names and complicated mechanical differences. The base-level system that comes with the V6 is called Quadra-Trac I, a single-speed, full-time four-wheel-drive that uses electronic clutches in the center differential to pass torque out to the front or rear wheels as needed for best traction. It works full time, so there are no switches, no buttons, and no handles to operate. It does not offer a low-range set of gear ratios.
The more flexible Quadra-Trac II (standard with the 4.7-liter V8) also uses electronic clutches in the center differential to distribute torque in High range, but adds a locking Low range. Both systems are slightly rear biased, with 52 percent of the torque normally going to the rear tires and 48 percent to the front.
Quadra-Drive II, Jeep's most sophisticated system, uses electronic limited-slip differentials (ELSD) at the front, center, and rear. ELSD replaces the Vari-Lock progressive axles in the Quadra-Drive system, with quicker response to changing conditions and greater torque capacity.
The SRT8 flat out flies, and it sounds terrific, too. Jeep claims it can thunder from 0 to 60 mph in less than 5 seconds, which is even faster than the Chrysler 300 and Dodge Charger SRT8s. Like those cars, the Jeep comes with a 6.1-liter Hemi V8. It is rated at 420 horsepower at 6200 rpm and 420 pound-feet at 4800 rpm in the Grand Cherokee, five horsepower less than in the Charger and 300. We loved the sound and found ourselves accelerating harder than necessary just to hear it. Throttle tip-in seems overly sensitive at times, causing us to leap off the line more abruptly than desired. At other times, it seemed slow on the uptake, but eventually we recalibrated our feet to enable smooth takeoffs from intersections. The throttle tip-in characteristics make the SRT8 less attractive as a commuter vehicle in stop-and-go traffic.
The SRT8 Hemi V8 features a higher compression ratio (10.3:1 vs. 9.6:1), a more aggressive cam, and higher-flow cylinder heads when compared with the standard Hemi. It's mated to its own super-duty five-speed automatic transmission and four-wheel-drive transfer case. The latter is a special unit put together from existing Jeep parts to optimize durability while minimizing weight. In normal conditions, it directs only five to 10 percent of the power to the front wheels, but it can redirect as much as needed to the front wheels to maintain traction. The rear axle is a Dana 44 with a tougher-than-standard ring gear and housing. Despite the high-performance parts, the SRT8 is rated to tow just 3,500 pounds, so think twice about ordering the fast one to pull your bass boat.
The SRT8 rides an inch lower than a standard Grand Cherokee, on specially tuned springs, shocks, bushings, and anti-roll bars. The ride is quite firm but not punishing. The steering geometry is altered for its high-performance mission. Forged 20-inch wheels come shod with Goodyear W-rated four-season tires with run-flat capability. Tire dimensions are P255/45/20 in the front, and a massive P285/40/20 in the rear. The brakes are upgraded with four-piston Brembo calipers (painted gloss red, as a decorative performance element that shows through the wheels) that clamp down on 14.2-inch vented rotors up front and 13.8-inch vented rotors in the rear. Jeep claims it can stop from 60 mph in less than 125 feet. We found the brakes effective, smooth and easy to modulate.
The SRT8's ride is quite firm and the steering is direct and very responsive. This is what you want when making time on back roads or blazing down a lonely highway at high speeds. It makes for tight handling, good transient response and high-speed stability. We're not sure we'd want it for everyday driving, however. The SRT8 was too jouncy for our tastes on rippled freeways in Los Angeles. It does a good job of filtering out roughness, but dips and other undulations make for uncomfortable cruising. And the steering is a bit darty for casual driving. But many drivers love it.