2005 WK was the first GC to feature the IFS.
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The Grand Cherokee (the ZJ series) was introduced in 1993 to replace the Wagoneer as a mid-sized luxury SUV (a luxury SUV that many companies would rush to imitate). The Grand Cherokee was the first Jeep to have the new Quadra-Coil suspension (now found on the TJ), the revised Quadra-Trac 4wd system, 4-wheel disc brakes, and an airbag. The ZJ also had 2 available V8's: the 318 5.2L and the rare 360 5.9L. The ZJ had its "big" redesign (and only redesign) in 1996 -- the most noticeable changes a new front fascia and new wheels.
In 1999 the Grand Cherokee saw a complete redesign from the ground up and was redesignated the "WJ". The WJ is bigger and more powerful than its predecessor, and has a 3-link rear suspension and improved steering geometry for better ride and handling. The WJ also features Jeep's new Quadra-Drive 4wd system with Vari-Lok axles and the new Quadra-Trac II system. The Jeep V8 also got redesigned and is now a 4.7L PowerTech putting out 235hp and 295 lb-ft of torque.
In 2005 the WJ Grand Cherokee was replaced with the new WK Grand Cherokee. A redesign from the ground up like its predecessor, the WK features IFS and an optional 5.7L HEMI powerplant. Jeep also introduced the SRT8 model of the WK which boasts a whopping 6.1L HEMI producing 415 horsepower (85 more horses and 25 percent more power than the 5.7-liter HEMI-equipped 2006 Jeep Grand Cherokee) and 410 lb.-ft. of torque which rockets the SRT8 WK from 0-60 in under 5 seconds, making it the fastest production SUV on the planet (even faster than the Porsche Cayenne).
Source:
http://www.jeepin.com/history.asp