Underbody Shield problems of the 2008 Toyota Tundra

My Tundra was making scraping noises when turning. Brought the truck to Toyota for service to find out the rear bearings on both sides were rusting out and they had to be replaced. Service representative said he called Toyota already even though my warranty had long passed. He stated that Toyota had increased the warranty on the bearings to a 5 year/65,000 miles. Toyota did pay about 1/4 th of the cost. Seems as though they know there is a defect in the bearing but not willing to cover the total cost of repair. This is the first time I have ever had bearing issues on any vehicle that I have owned. I drive most of my vehicles for about 8 years or more. Thus one of the reasons I buy Toyotas. Not sure if that will be true any longer.