I have gone through the analysis for the 2015 KR that I plan to order in Feb.
I made an Excel spreadsheet but don't know how to attach.
With 20" tires and 3.31, 60mph = 1487, 70mph= 1735, 80mph= 1982 rpm.
with 20" tires and 3.73, 60mph = 1675, 70mph = 1955, 80mph = 2234 rpm.
I have decided on the 3.73 because
. Even with the the 3.73, The EXP is longer geared than my 2000 Explorer with a 3.55 due to larger tires.
. Even though the highway revs may be higher, you are likely to be less into the boost minimizing the economy loss.
. Around town, you will be in top gear sooner with the 3.73 than the 3.31.
. The Navigator which weighs about the same as a loaded EXP comes with the 3.73 standard.
As an aside, the Navigator is rated 380hp/440ft# because they specify Premium Fuel. My guess is the EXP will get the same output as the knock sensor compensates for Premium fuel.
mreed112,
Fine points in Bold indeed! I was wondering what the tradeoffs were. Most of my towing would be through rolling hill areas to SW Texas towing my 14' flatbed with my RZR XP900 4-seater to the ranch maybe 10x/year, 5 hours each way. The weight wasn't a big concern for me, but having the truck in the sweet spot of the power band while cruising was important.
Right now, my Nissan which has 6" lift and 34.5" tires has 3.3751 gears and it pulls hard with the Bully Dog installed, but tends to shift ALOT when pulling the RZR. If the 3.73 will minimize that, I'm sure my fuel economy will be better. That happens maybe 10x each year, so max 6,000 miles per year in that role.
If the wife has it on certain days, the Expedition will be used in town taking kids to school/pick up about 3,000 miles/yr. Then, for going to and from work and to projects, I may put an avg of 55 miles/day (MWF), so maybe 8,000 miles/yr.
SO, I think you may have changed my mind if the difference is only 220-250 rpm between the 3.73 and the 3.31's. You're right, the Navigator get's the 3.73 standard, with the option for the 4.10's, yet "advertises" the same MPG!!
