We towed a Lance 1685 21' trailer (3700# dry; approx 5000 loaded) with our 2006 6 cyl Toyota 4 Runner for 10,000 miles. We already had the truck, husband said I could have a trailer but not a new truck. :( We were lucky not to have any problems (but we re-routed to avoid Wolf Creek Pass, CO in a May blizzard). Before you decide to make a similar decision, be sure to read:
Dark Side of Towing With a Toyota 4 RunnerWe've since upgraded to a Toyota Tundra. The difference is feeling every little movement of the trailer with the 4 Runner versus not even knowing the trailer is back there with the Tundra.