Dial Herco

Mayer also believes that The Grapevine claims many vehicles “that are inadequately geared.” By this he means that vehicle owners are running the wrong size of differential gears.
Let’s say the truck is fitted with a rear-axle ratio of 3.08:1, which is fairly common. This gear ratio ensures good fuel economy but may not deliver enough power to the rear wheels for optimum towing performance. The end result is a lagging engine and a hot transmission—a deadly combination.
But a truck equipped with a lower axle ratio (4.10:1, for example) can pull a load more easily with less heat buildup. This is especially important if your truck pulls heavier loads such as big bass boats. The trade-off is higher fuel consumption, which is still cheaper than rebuilding a transmission.