Just my experience with gearing....below is my 2007 E350. V-10, 5 speed torqshift tranny on 33" tires and it came from the factory with 3.73 gears. I drove it that way for a couple years and was never happy because the tranny would shift down on every grade no matter how gradual it was. Worst part was, because it spends most of its time on dirt roads at 45-50 mph the tranny was constantly shifting in and out of overdrive. Mileage was steady at 12 mpg whether I was driving 45 mph on dirt or 75 on the highway. On the advice of a local 4x4 shop I had the gearing changed to 4.56 - and I couldn't be happier. The constant shifting problem is gone and the van is just much more responsive. Several years later and with nearly 60,000 miles on her my overall mileage - 12 mpg!
