How to use Overdrive on your RV
The easiest way to think of overdrive is to associate the word “overdrive” with the phrase “real high gear.”
Once you establish this mental picture, all confusion disappears. Overdrive means you use the largest gear in your transmission to turn the wheels at high speed. Because the large gear has more metal teeth than the smaller gear, the large gear must spin less (less RPM) to maintain the same speed as the smaller gear.
So when you’re driving at a higher speed, it would make sense that you’d get better fuel economy because you’re being driven by a larger gear that spins less. Overdrive reduces engine RPM and this saves gas and engine wear. Overdrive is best for long, flat stretches of highway. I always start speeding when I know the road in front of me is not hilly and I will be able to drive continuously at high speed on the highway and I am not towing or carrying an extra heavy load.
You can also just leave the overdrive switch on and it will happen automatically. I recommend overdrive for speeds of 60 MPH or higher. When should you NOT use it? Never use acceleration when driving in hilly areas, towing something or traveling very slowly. You can actually damage your transmission if you do. Remember that the large gear must rotate less to maintain the same speed as the smaller gear. So at higher speeds, the big gear does its job, pushing you effortlessly down a long flat highway at a constant high speed and saving you gas while doing it.
But when you’re traveling at lower speeds or stop and go or going up and down hills or towing a car, it’s less about high-speed point-and-shoot travel and more about quick power to accelerate or the ability to navigate through hills or mountains or be able to safely tow a heavy load. At a lower speed, the large gear will turn less and less and lose its efficiency compared to the smaller gear.
You will then need to downshift to generate enough rpm to provide power to the wheels. If you don’t downshift, you will quickly feel that the larger gear is struggling to drive the wheels and the RV will vibrate and shake. You should never use overdrive when driving in these more stressful conditions. I leave the acceleration off and manually flip the switch to “on” when traveling long stretches of flat highway.
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