The all-new WK Grand Cherokee debuted in 2004 for the 2005 model year. Features available for the first time in a Jeep included Quadra-Drive II four-wheel drive, rear-seat DVD player and optional 5.7L Hemi V8. The 3.7L V6 engine replaced the 4.0L Straight-6.

The design still emphasizes power and luxury, with significant work done on improving noise, vibration, and harshness (NVH). However, for the first time, Jeep also emphasized on-road performance to a similar extent as the cornerstone of its brand, off-road capability.

This newfound emphasis on on-road refinement led Jeep to replace the live-axle with leading-arms front suspension (found in the ZJ and WJ) with a new design: an independent double-wishbone setup like that which debuted in the 2002 Liberty. The new Jeep changed its philosophy due to what it perceived as increasing demand in the SUV marketplace for on-road performance and decreasing demand for off-road capability, and though the new design is perceived to be more smooth over washboard-types of roads, the new front suspension was criticized by off-roading Jeep community for its inability to provide optimal axle articulation during low-speed, technical maneuvers, specifically over uneven terrain.

The 2007 Jeep Grand Cherokee made its European debut at the Euro Camp Jeep held in Ardèche, France.

The Grand Cherokee received a minor facelift for 2008. The bottom part of the headlights became rounded, and the lower portion of the front bumper became removable to increase the approach angle for off-road use. The 4.7L was refined, now producing 305 horsepower, and 334 lb·ft (453 N·m).

The 2009 Jeep Grand Cherokee is available with an improved 5.7-liter HEMI rated at 357 horsepower (266 kW) and 389 ft·lbf (527 N·m). (527 N•m) of torque. The engine uses variable valve timing to increase fuel economy.
From Wikipedia