[Bill]

Regarding the manufacturer's instructions re towing in overdrive - jniles is right - and so is CCTurtles. And most likely, so is Camperboy. The instructions apparently vary with manufacturer, model, and year. The owner's manual for my Ford Explorer, for example, specifically states that it is OK to leave the overdrive on, unless the transmission starts to "hunt" - i.e., shift up and down a lot. I have confirmed this on the web - but even some Ford mechanics weren't aware of it until I pointed it out to them. It is apparently a new rule.

Since the day that automatic transmissions were invented, the general rule has been to "turn the overdrive off when towing", and many people cling to that rule like a religion. But despite the sexy name OVERDRIVE (which was invented long before automatic transmissions came on the scene, by the way), there is nothing magic about "overdrive". It is just another gear, just like 2nd gear or 3rd or 4th gear. And you don't want the transmission to be shifting a lot between ANY two gears. If you turn overdrive off, and get into some mountains, and your transmission starts shifting a lot between 2nd and 3rd, then you are harming your tranny just as much as you would if you were in flatter country and your tranny was hunting between 3rd and 4th gears. In this case, you have already turned off 4th gear (overdrive), and now you should "turn off" 3rd gear by moving the shift lever to 2nd.

So the best advice is simply to be aware of what your transmission is doing! If it is shifting a lot, then turn off the overdrive. If the terrain gets steeper, and it again starts shifting a lot, then use the shift lever to drop down another gear. The goal isn't to adhere to some vague and poorly-understood rule - it is to keep the transmission from hunting. And by the same token, if you come down out of the Rockies and head east through Colorado, then by all means turn the overdrive back on and save some gas.

Bill