2007 Jeep Grand Cherokee 3.0L CRD

The Ford Explorer may get the credit for being the first popular midsize SUV, but the Grand Cherokee has proved to be the real 4x4 king of that class since its debut in 1993. While the Explorer has become a bloated, independent-rear-suspension, kid-hauling parody of itself, this Jeep is still a real 4x4. Sure, it may have lost some hard-core fans when the front axle softened with the '05 redesign, but the capability of the Quadra-Drive II system, the comfortable ride, and the superb new diesel drivetrain make this one of the best 4x4 trucks to drive on- or off-road.

Ever heard of a valve-cover cover? Dense rubber (similar to the material used to make those stress-relieving squeeze balls) is molded to fit around the common rails, fuel lines, and injectors to muffle noise created by fuel injections and the DOHC valvetrain.

The 3.0L CRD V-6 EngineA 3.0L V-6 is being used to power a 4,750-pound SUV? That may sound crazy, but this Mercedes-Benz diesel mill can easily put out 198 hp and 371 lb-ft of torque to all four wheels. The engine is all aluminum alloy-except for cast-in, gray, iron cylinder liners-and uses the latest high-pressure, common-rail fueling system by Bosch along with fast piezo-actuated injectors. Up to 24,000 psi of fuel pressure is combined with the intercooled output of a variable-geometry Garrett GT2056V turbo that kicks in hard at just below 2,000 rpm. A 3-inch downpipe sends exhaust through an oxidation catalyst, a NOX-reducing catalyst, and a diesel particulate filter (just like in the new fullsize trucks), allowing it to be sold in 45 states.

W5J400 Five-Speed AutomaticPower from the turbodiesel is handled by the W5J400 five-speed automatic with manual shift mode that's built in Germany. It's not easy handling more than 370 lb-ft of torque, but this automatic does it in style, shifting smoothly during light-duty driving, and banging the gears when you mash the throttle pedal. Flicking the shift knob to the right or left engages manual shifting, with the gear selection displayed inside the tachometer dial. There's no point in trying to outshift the transmission during hard acceleration (you're bound to shift too early or hit the rev limiter), but the manual mode is terrific for driving on steep mountain roads. Downshifts provide superb gear braking (it feels like the turbo is also helping), and by keeping the engine around 2,000 rpm, you can guarantee instant, neck-snapping acceleration at any speed.

A variable-geometry Garrett GT2056V turbo suffers from some lag when the engine is spinning at less than 1,800 rpm. Wait until the 3.0L is turning 2,000 rpm, then floor it, and the boost hits like an NFL linebacker from the time it kicks in all the way up to the 4,500-rpm redline.

Performance TestsBuilding boost up to that magical rpm while holding the brakes provided our best quarter-mile times during testing at Los Angeles County Raceway. The front tires squealed as they broke traction before the differentials locked up and put all the power to the ground for a fastest elapsed time of 16.182 seconds at more than 81 mph (15.939 seconds at 82 mph-altitude corrected). The all-wheel-drive experts at Yimi Sport Tuning confirmed that 198 hp and 371 lb-ft of torque is consistently sent to all four wheels. Noise testing revealed the Grand Cherokee is a bit louder than the newest fullsize diesel trucks, but fans of the Jeep Liberty diesel will notice this engine is much quieter than its 2.8L Italian cousin. Fuel-economy tests showed this engine with less than 4,000 miles of use was capable of nearly 18 mpg in combined driving conditions, including dragstrip racing and Low range off-roading.

Off-Road Diesel PowerThe Jeep felt at home when the all-terrain tires hit the dirt, but this luxury rig was definitely not built for jumping. Low-hanging bumpers are easy to snag on obstacles and greatly reduce the approach and departure angles, so rockcrawling is out of the question. That's OK because a stock Grand Cherokee is built for getting to your campsite, not for blazing trails into uncharted territories. The Quadra-Drive II system is standard with 4WD diesel models and can send power to all four wheels at any speed. A simple grab of the 4WD Low lever next to the shifter provides quick and easy access to the 2.72:1 Low range gearing, which works perfectly with the low-rpm torque of the 3.0L CRD engine.

To help keep the smooth-running Mercedes-Benz engine quiet, the plastic engine cover has a thick layer of sound-deadening cloth. Sound insulation can also be found on the firewall between the engine and the driver.