I have a 2004 Suburban 2500 with the 6.0 liter and automatic transmission. I tow a 33 ft travel trailer with a dry weight of 6250. I recently weighed the whole rig and came in at 14460 lbs. I tow in 3rd gear with the Tow/Haul mode on. Most of my towing has been low country to the beach and to Florida and back to the upstate of SC where we live. If I use the cruis control the engine seems to rev a good bit to try to keep up the speed. I have stopped using this except on the flatest of roads. I recently towed it to NC , Virginia, Washington DC and on up into New York state and back. Crosing from NC into Virginia to the Shannadoah region I drove up a 13 % grade. About 3/4 of the way up the transmission temperature gauge got into the red. When I got to the top I pulled over, opened the hood and let it cool for half an hour (while still running). There were some other smaller grades along the way 6 and 7%. I have read specs that say this suburban should be able to tow 10,000 lbs. I would not feel comfortable doing so knowing that the trailer I pull feels musch heavier than it actually is while I am towing it. (I do use weight distribution and sway bars). Does anyone else have a similar rig they could share information as to whether this rig should be OK in mountains. Has anyone had any issues I need to be looking for?