According to RV technical writer Bill Farlow, it is not uncommon for the light diesels used in small trucks to go 250,000 to 300,000 miles before overhaul. Engines in heavy trucks often exceed these numbers by hundreds of thousands of miles. All these add up to real economy. When shopping for a vehicle, it's important to know and ask about its gear ratio. So here's a quick and somewhat simplified overview of gear ratios and why they are important when it comes to towing.
Engines turn fast to develop horsepower.
But if the truck's rear wheels were connected to the engine, you would find that the engine couldn't develop any power. Therefore, gears are used to turn the wheels more slowly than the engine. Rear end gears reduce speed, and the gear ratio indicates the amount of this reduction. A ratio of 4.10 means the engine turns 4.10 times as fast as the wheels. So when looking for a tow vehicle, remember, a high numerical ratio gives more towing power than a low numerical ratio.