Usually two - on the front wheels.
In the brake rotors.
you can get the whole package on ebay for under $200.....Callahan Brakes and rotors.. Just type in 2002 Jeep Grand Cherokee Laredo brakes in the search on eBay
The grand Cherokee does have four wheel disc brakes. The wrangler and Cherokee have rear drum brakes.
The 2014 Jeep Cherokee has 16 valves.
The 2007 Jeep Grand-Cherokee has 12 valves.
The 2006 Jeep Grand-Cherokee has 12 valves.
The 2008 Jeep Grand-Cherokee has 12 valves.
The 2001 Jeep Grand-Cherokee has 12 valves.
The 2003 Jeep Grand-Cherokee has 12 valves.
The 2002 Jeep Grand-Cherokee has 12 valves.
The 2014 Jeep Grand-Cherokee has 24 valves.
The 2013 Jeep Grand-Cherokee has 24 valves.