Would throwing in an aftermarket tranny cooler with a fan help enough? I don't trailer much, but on the beaches, I've had my tranny overheat a bit so I looked a bit at the B&M coolers.
I did pull a single-axle trailer with 2500-3000 lbs on it 600 miles last Nov, had no issues with overheating.
2011 Nat Green Rubicon Unlimited, RR XHD Front & Rear, Warn M8000, Rock Hard 4x4 Rails, Flipped Mirror, Cobra 75 CB, MyGIG & Infinity, NAV, Homemade Bikini Top, 35x12.5x17 Toyo MTs on ATX Crawls w/ 0" offset (4.5" B.S.) with trimmed fenders, small lift needed soon.