Tranny problems are mostly on the 4spd. The 6spd is much stronger. Only complaints I here about it are the way it shifts which can be fixed with a tune. I have driven one and can say I didn't like the way it shifted in the trucks compared to the cars I have driven that had it. Yes the 6.0 was an option in the suburban but I don't think there are many out there and the 6.0 is basically dead now. Autoride is a great feature when it works if it goes out though be ready to spend the big bucks to fix it. I had a problem with mine but luckily the extended warranty company covered it all.