Quote:
Originally Posted by ShadeTreeMech
What I have found is if you can stay in overdrive, do so. This will of course entail a speed bleed, otherwise you will downshift and it's all lost.
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I disagree, because my own testing has repeatedly proven, in a variety of applications, that 200 RPM too much is better than 50 RPM not enough.
Now, if one is willing to add axle ratio to enable staying in OD, then that matches my findings. But most of my testing has been in hilly to mountainous country.
For example, I had an '06 GMC Sierra RCLB 2WD 4.3L, a/t, 3.23:1, did a regular best hwy avg of 20 MPG. It wouldn't quite hold 3rd when towing on flat land. I should have gone 3.73:1, but even after swapping in the 4.10:1 rear axle and getting its computer recalibrated, my MPG improved to 22 nearly all the time. Further, my acceleration and towing both improved dramatically, and it did end the downshifting out of OD for grades when empty. And I can give other examples.