Originally Posted by ttrost65
My maiden voyage after owning my 365 for a solid 48hrs was towing it to Ft Myers Beach and my duramax did wonders. I ran 70mph almost all the way and got 10.5mpg down and back. It pulled much easier than the 6800lb TT that I had towing with a '06 2500HD 6.0. I don't have knowledge on how your big gasser is going to handle your 5er, but the truck frame is solid and has NO problems towing the load. I know I wasn't comfortable towing my "little" trailer with the gasser that I had, but then the newer trucks do much better. You should be fine for the trips you mention.
My former 09 2500HD 6.0 had a workout towing our previous 9500lb TT, fine on flats but hills were changing gears like crazy and horrible gas mileage (7mpg).
The 6.6 TD we have now tows the heavier Sabre (12K loaded) with no problems at all, couldn't imagine trying that with the gasser though the GM frame could handle it.
BTW, Allison transmission only comes with the Duramax Diesel.