Okay, you are talking about a 13 year old vehicle with 170K miles on it. A lemon usually is a fairly new car that has an irreparable problem and is bought back by the manufacturer and swapped out for a new one. Other than tranny failures, which are common on the Chevy trucks, you haven't had too many really big problems with this truck.

What do you use it for? Do you tow anything with it? If you are towing and you just stick it in drive and take off with a heavy load, you will most assuredly fry your tranny in this truck. This transmission is not meant to be used in overdrive while towing and will fail prematurely if you do so. With every Chevy I have owned, I have towed in 3rd gear and they have had no tranny issues. Even a snowmobile trailer with two sleds on it is more than you should be towing in OD.