19/09/2008 11:13. Jim has been tackling trails in one 4WD vehicle or another for 31 years. For the last 15 or so years as the founder and president of Dynatrac in Huntington Beach, he has been helping others tackle trails as well. Dynatrac manufactures some of the stoutest axle assemblies on the market, including its Trail Series Dana 44 and 60 units and its widely recognized ProRock 60, which has been turning competitive rockcrawlers into champions since its 2002 release. Since Jim's goal with his Jeep Unlimited was to attack tight, rock-strewn trails that he wouldn't attempt in his truck, he installed a set of the venerable ProRock 60 assemblies. Both the front and rear ProRock 60s offer more ground clearance than a Dana 44 and are built for abuse, using 40-spline axleshafts, 5.38 gears, and Detroit... // 4 Wheel Drive & Sport Utility Magazine