You shouldn't expect trouble with an "old truck" if you maintain it properly. We just loaned @ccreddell our 2000 1500 Suburban and our 12k trailer to go after a 400 parts truck in Rexburg, ID, a trip of almost 800 miles one way. He was over 15k coming back. No issues at all even with 270k and still on the original 4L60E. It will get an oil change shortly (I do it every 5k) and the transmission fluid is just starting to turn color so we'll service the transmission when we do the oil change. Yes, the 5.3 was working its butt off but we expected it to be smooth and it was.