[kaisen]

If you're intent on a 2003-2006, I'd buy a Navigator with the ZF 6 speed instead of the old Ford-built 4 speed A4OD-E in the Expedition of those same years. Huge difference.

Also, the early (03-08) 3v 5.4L was notorious for failed cam phasers that made the engine sound like a diesel at under 1500rpm. You'd know in the first minute at idle. Need to remove front accessories, replace both phasers (L, R) and timing chains. Most 03-06 have had this done by now. Perhaps several times.

If it has four corner load leveling, make sure you inspect the air compressor and all four air reservoirs for leaks and operation. Check by putting it in four-low and see if it raises, then immediately into 2wd then park to see if it kneels.