I have a Ford Hi-Rider that gets terrible mileage when pushed hard. Seems to be turning too many RPMs. Anyone had experience with getting the dealer or shop to change the differential?

I have a Ford Hi-Rider that gets terrible mileage when pushed hard. Seems to be turning too many RPMs. Anyone had experience with getting the dealer or shop to change the differential?

I've had the rear differential ratio changed in a couple of trucks, once to fix a broken diff, from 3.88 to 4.11 and the 2nd time just to get the higher top speed. I can't remember the exact ratio, but I had it done by an independant shop both times. I would never go to a dealer for something relatively simple like that.

But you won't get fuel economy improvements by going faster at the same RPMs, there are no free rides, remember:

Drag should be proportional to the square of speed.

R ? v2

This pick up turns about 3000 RPM at 100 km/hr.

I have a company pick up (Isuzu) that turns about 2500 at 100.

The Ford's top end is about 145 kph and really burns diesel at high speeds.