I pull a 30-foot Surveyor with my 5.4L Expedition. It does well. HOWEVER, you should be aware of a very common problem with the 5.4L Triton....it will blow spark plugs! When the aluminum heads get too hot, the spark-plug threads get soft, and one of the eight may let go and launch. Google "Ford 5.4 Triton spark plug" and read for yourself.
< Chevy fans, insert your trash-talk here. But, you are wasting your time with this member >
We are a long-time Ford family, we love our Expedition, and we want to keep it. Here is how I make sure I keep it for a long time 1) Keep below 3,000 RPM as much as possible when towing. 2) Idle the engine when at rest stops to keep the water pump on; this will keep the aluminum heads cool. 3) Find a speed where the automatic transmission can visit overdrive often; running full time in 3rd gear is a sign of hard work. 4) Overall, keep the gas pedal off the floor when accelerating or climbing.
Even with these tips I can pull my 30-foot Surveyor at 70 MPH in 4th-gear-lock-up on the Interstate, and climb 6% grades in the Rockies at 45 MPH in 2nd gear at 3,000 RPM while driving at 8,000 feet in elevation. So far, 115K miles and no calls to AAA