|
After plenty of experience replacing "economy" axle ratios with the next ratio up, numerically, I can give it as tested and proven fact that lowest possible cruise RPM is NOT always best. Better to have 200 RPM extra than 50 RPM not enough. So you may find a real improvement by going to the salvage yard, getting a 3.54:1-geared axle for $160, bolting it in one Saturday afternoon, then Monday morning getting your local stealership to switch the calibration. Trying to get such a small engine to pull such low RPM in such a draggy vehicle is silly to begin with.
Also, you may need 4WD, but is it just for traction, or do you also need the ground clearance? If not, lower the truck. Cutting coils isn't ideal, but it is cheapest to do, and cheapest to undo, for testing. But you'll need a front end alignment once lowered, and again if you don't like lowered.
Contrary to Mythbusters testing, which was only one truck, some other trucks do benefit from tailgate down, others from tonneaus. You'll have to do your own testing to determine what yours likes.
I'd trade it for a RCLB 5.2L Dakota and work from there. Just the reduced drag would give at least 5 MPG.
|