Posted: 10/7/2008 4:51:38 PM EDT
|
What is it, and should I leave it on or turn it off? I've got a Jeep Libery, btw (not sure if it matters or not). |
|
Overdrive is the highest (numerically lowest) gear in a transmission that allows the engine to spin at reduced RPM at highway speeds, in the interest of increasing fuel mileage and reducing wear and tear on the engine and drivetrain. Typically, you should disable overdrive if you're hauling/towing something and/or the transmission is constantly hunting between gears, like when driving in hilly areas or again when towing a load. |
|
An overdrive is a gear that causes the output shaft to turn faster than the input shaft. This provides a great increase in economy at high speed compared to a non overdrive top gear which would be direct drive, meaning that the input and output shafts are turning at the same speed. The drawback to overdrive is that it produces very little torque, which is why your transmission has to downshift when you want to pass. The only reason you would want to turn it off is as stated already, you are towing or climbing a steep grade and the transmission isn't able to stay in overdrive causing constant up and down shifting, which will overheat the transmission very quickly. |
Well, I'm heading up to the White Mountains tomorrow, so I'll have to remember to turn that sucker off when I start hitting those steep grades. Thanks again, guys. |