Hauling my trailer

With the OP not telling us anything specific about the particular truck in question who's to say how capable (or not) it may be negotiating serious upgrades? :h I tow with a 5.3L Avalanche equipped with GM's ubiquitous non-tow friendly 3.42 axle ratio and because it has the older wide ratio 4-spd transmission I always tow our 4500 lb 20' travel trailer in 3rd with Tow / Haul engaged. Towing in Drive even over relatively flat terrain results in too much unintended downshifting and serious upgrades require a downshift to 2nd. Newer GM 1/2 tons that produce even more power, are coupled to a much better narrow ratio 6-speed transmission, and which are equipped with a tow friendly 3.73 axle ratio would do much better. Bottom line - no one can answer the OP's question with any degree of certainty unless more specific information about this particular truck is provided.