Heaviest load so far was a 750lb aluminum trailer with a 2010 Kawasaki Trans4x4 Mule Diesel (about 2,200lbs including winch, bumpers, roof, stereo, etc). We also had three 200+ lb guys in the Runner.
The 4Runner did fine— particularly considering I was not able to hook up the trailer brakes (or brake lights) due to the asinine way the trailer plug is mounted on the Runner. I'll plan ahead next time and make a pigtail. I manually shifted to keep the truck in the torque curve. I was completely satisfied with the power and the Runner's ability to manage 3,000lbs.
That said, I would definitely put the 4Runner in the category of being capable of towing, but not specifically well-suited for towing. This isn't a bad thing, none of us bought 4Runners to be cross-country horse haulers. Coming from a guy whose last vehicle was a 2008 GMC Sierra Denali with the 403hp 6.2L V8, you definitely see the difference between a truck that is CAPABLE of towing and a truck that is DESIGNED for towing.
Although I feel the frame and platform are plenty competent in the 4Runner (especially with Airlift!), the lack of low-end torque in our trusty V6 becomes evident when you load up the weight.
This is especially the case for those, like myself, who have added larger / heavier tires and a lift to ensure our vehicles look and perform as awesome as we know they are.
