[masraum]

Originally Posted by oldE

Neat idea! I've been tempted to do the same with the F-150.

Not sure why you are thinking you are getting a reduction in RPMs at speed since that would happen only if your torque converter (automatic tranny, right?) had been slipping or you were running larger tires.

Any mpg increases whould come from reduced throttle openings due to lower horsepower requirements at lower drag levels.

Keep up the good work!

Les

Won't a torque converter "slip" some (unless it's a lock-up model) based on load. As far as I know, a torque converter's lock up is not based on anything rigidly mechanical like gears. It's based on fluid and viscosity and load, so if you take a 3000 stall torque converter and hook it up to a car with 150 lbft of torque and 3000#s and then to another with 600 lbft of torque and weighing 4000#s, the stall speed will be higher on the heavier higher hp/tq vehicle.

I don't know if that lip is enough to make a big enough difference in drag to make a 200 rpm difference at speed, but theoretically, it is possible.