I can tell you they weren't a result of inadequate maintenance. MAG didnt play around with warranty claims. You had to have every service done to get warranty work. The number one thing, that I always saw in Service was the diff's, second runner up was the exhaust manifolds.
Most owners of these, will most likely have service records. And if your lucky and nice enough, you may be able to sweet talk someone at MAG into reviewing services performed with the VIN.
When I worked there I had to pay for the 20k service to get a reverse gear warrantied at 31k. The only reason I got that, was because I was an employee. If I was a walk in, I'd have been paying for a full rebuild.