Fuel economy with a regearing?

[scraph]

I have a 2000 F-250 with the 6-speed manual transmission. In city driving I get just over 19mpg (this is with continuous stop-and-go and playing around with the turbo somewhat). In highway driving (~70-75mph) I only manage to get 16mpg.

I have 3.73 gears and stock size tires (265/75R16) and at 75mph my engine is turning 2200rpm. I imagine the reason for my poorer highway economy has to be due to this higher sustained RPM and therefore due to the 3.73 gears.

I do use the truck for some towing, however, the largest load it will ever see for the forseeable future is a 4000lb 20' boat. I imagine I would still have plenty of pulling power available for such a light load if I regear.

Does anyone have any recommendations as far as new gear ratio in consideration of pulling the boat, maintaining good fuel economy in the city (should only improve/maintain with higher gears), and improving it on the highway.

Thanks.

[mrnecsteve]

I have no personal experience with these ....but your truck could be a candidate for one of these:
http://www.forddoctorsdts.com/articl...icle-05-01.php
Overdrive for Ford E4OD & 4R100 4 speed automatics Save Money!
When they offer one suitable for the f250 6.0 with transfer case ,i intend on getting one or the other.
If you do a "payoff analysys" dont be short sighted...you can do the install with the thought of taking it with you to your next truck ,years down the road. or reselling it with your truck at a markup. (Keep your original parts AND modify a junk yard driveshaft that you recondition)\
I dont have personal experience with your engine. I am certain that mileage drops off
big time ,when i cross over the sweet spot of 2000 rpm on my 6.0. Hopefully others will chime in what there experience has been with your model engine.

[sirnunya]

under 2000rpms is where you'll wanna be. If you have a 4x4 I think the only other option is 3.54 gears, if you are only 2wd you could go down to 3.08's. There is a guy on here with 3.08's, but he has a single cab 2wd with some fairings and whatnot to achieve max mpg. Paying someone else to change the gears is not cheap either, so I would look into that. Another way to drop the RPMs would be to put on bigger tires. But that would increase rolling resistance and city mileage will go down but highway should go up. If you're only 2wd I would do it, but changing out two is $$$$. Maybe I'm just cheap