Dear Tom and Ray:

On my 1991 Camry, there's a button called "overdrive." Can you please explain to me its functions and usage? -- Mike

Tom: Yes, Mike. That's the mother-in-law ejection seat. But it only works once, Mike, so make sure you wait until she's in the middle of a good, loud rant before you hit the button.

Ray: Actually, overdrive is just another name for fourth gear on your car. Overdrive is a gear designed for high-speed driving. It provides little power to accelerate, but allows the engine to run relatively slowly so you get excellent gas mileage.

Tom: And that button is there to turn overdrive OFF. Now, at this point, you may be asking yourself, "If I have an automatic transmission which chooses my gears for me automatically, why would I ever want to turn overdrive off?" That's a very good question, Mike! And in most cases, you don't want to turn it off.

Ray: There's only one exception, really. There may be certain road or traffic conditions that force you to maintain a speed that keeps the transmission right on the hairy edge between third gear and overdrive. That speed is generally about 35 mph. And at that speed, the transmission tends to "hunt." That means it goes back and forth between third and overdrive trying to find the right gear to be in.

Ray: Is that bad for the car? Not particularly. But it can be annoying to the driver and passengers. And that's why that overdrive button is there. So when the transmission is "hunting," you can turn off overdrive and force the transmission to stay in third gear until your driving conditions change.

Tom: Other than that situation, I would suggest you just ignore the overdrive button, as you've obviously done quite successfully since 1991, Mike.

What's the best way to warm up your engine in the morning? Find out by ordering Tom and Ray's pamphlet "Ten Ways You May Be Ruining Your Car Without Even Knowing It!" To order, send (check or money order) to Ruin, P.O. Box 536475, Orlando, FL 32853-6475. You can also order online.

© 1997 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.

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