2011 w/ F&R bumpers, winch, 40 gal Aux Fuel, Drawers, tools, RTT, etc. and it tows just fine - its not gonna tow like a newer diesel, but itll move. Keep it in manual mode and in 4th (08-15) or 6th (16+) so it doesnt hunt gears.
I also have heavy rear coils and AirbagMan HP Bags