I've got a '98 xj with 4.0, AW-4, 3.55 gears, D-30, Ch 8 1/4, 31' all terrains, a good weight distributing hitch and an aux tranny cooler.
I've been towing a boat that is 3200# plus the trailer - and with other stuff I'm sure is pushing right up close to 5000#.
This all works reasonably well...