My 13 Outdoorsman was one year too early for the 8 speed. I had the 6 spd and 3.92. The engine and trans towed my trailer like a dream. round trip Michigan to Alaska and Michigan to Death Valley, so LOTS of mountains, never short on power. Only once did I back off the throttle up a grade, I dont recall the road, it was westbound uphill grade between Vegas and Death Valley. Despite December, it was nearly 100F outside, with a headwind blowing East. I saw my trans temp climb significantly holding 60mph in maybe 3rd gear? Dropped down to 40mph for the rest of the climb, temps dropped, crested the grade and back to 60 no more issues.
My only complaint was payload. The Outdoorsman has so many bells and whistles, even with the smaller 4 door cab (the discontinued quad cab), I had 1200 payload. The rear springs were so very soft, even 500lb tonque had it squatting badly.
Trading in for the Tradesmen 2500 took some adjusting, I sometimes miss all the creature comforts the Outdoorsman package offered. But the price was almost the same between trucks, and an extra 2100 lbs payload help me get over the loss of creature comforts.