A number of 2004 Arctic Cat ZR 900 owners experienced durability issues with the new ACT Diamond Drive gearbox. After a thorough investigation, Arctic Cat determined an improper heat treatment was used during the manufacturing of the ACT driveshaft, allowing the driveshaft to break. Sources indicate this affected approximately 25% of the driveshafts.
While the consensus appears to indicate this was strictly a process and materials issue and not a design issue, Arctic Cat has upgraded both the manufacturing processes and design to exceed their own specification standards. Changes to the design and manufacturing include an upgraded heat treatment, an increase in the thickness of the wall area surrounding the spline area, a new coupler with locking pins instead of locking balls, and an improved material quality specification.
These changes are expected to be implemented on all 2004 ZR 900s, as well as all 2005 Arctic Cats that feature the ACT drive system. Owners of 2004 ZR 900s should consult with their dealer for details surrounding the upgrade of existing units, involving the replacement of the driveshaft.