[Pyrotechnic]

4L60E - 3.06 1.62 1.00 0.70

4L80E - 2.48 1.48 1.00 0.75

When concerning gas mileage, the overdrive gear in a 4L80E won't drop as much RPM as a 4L60E, so a numerically lower gear would be better for a 4L80E...if cruising RPM's and gas mileage are your main concern.

When concerning acceleration or pulling ability in first gear, a numerically higher gear would be better for the 4L80E because of it's higher first gear.

The biggest thing to prevent constant downshifting is to consider the terrain and payload against the power your engine produces at lower RPM's.

For example if you never intend to tow and you live in a mostly flat area, you can get by with cruising at a low RPM. If you intend to really load the truck down or you live in an area with a lot of hills, then you will want the engine to run at a higher RPM in overdrive.

Also consider tire size. The difference between a 26" tall tire and a 31" tall tire is pretty significant.

In general for most stock to mild V8's if 65-70 MPH ends up around 2000 RPM or a little more, you will be fine. It is possible to go lower and many new truck do go lower than that, but you must carefully consider the torque curve and the intended use of the truck.