I have a 2004 Silverado 1500 5.3L V8, Automatic with 78,XXX miles. Been having problems with my transmission for about a week now.. The transmission seems to be shifting weird from second into third.. almost like it takes a while to shift or it might be slipping. I just changed my transmission fluid and filter about 10,000 miles ago. I had a friend of mine who owns a transmission shop do it.. I'm 100% sure he used the correct fluid and filter, and the level is right where it's suppose to be.. I added some "Lucas Transmission Fluid Stabilizer" to it today, but it didn't seem to help much. Is there any kind of warranty extension for the transmission on these vehicles? Or does GM pretty much tell their loyal customers that it's normal for a transmission to fail after 78,XXX miles of normal use???