Tire Valve problems of the 2007 Jeep Wrangler

Tire valve stem failures, stem mdl tr-413, original factory wheels/tires on 2007 Jeep Wrangler purchased in February 2007. Rt front tire went flat while parked. Noticed the valve stem was separating. Check other tires and left front stem was also split and hissed when flexed. Jeep dealership said it was not covered under warranty and said to contact tire manufacturer when my son called them. I called and left msg for dealership service manager who never returned call. Took vehicle to a local tire shop and all five stems replaced. All five are mdl tr-413. Vehicle owned by my son.