what is overdrive?

Question

what is overdrive for in a car? when is it suppose to be on? and when is it suppose to be off? is it bad if i leave it on all the time? thankyou

Answer 1

"5th gear" for your automatic. Leave it on all the time for economy. The only time you would turn it off would be if you were pulling a heavy trailer, or doing mountain driving and needed the extra braking power.

Answer 2

To put it simply, overdrive is a gear with a ratio of less than 1:1. A typical overdrive will have a ratio of about .74:1 or so. A 1:1 ratio means that the output shaft of the transmission is turning the same RPM as the engine crankshaft. Overdrive means that the output shaft of the trans is turning faster than the crankshaft. It is O.K. to leave the overdrive on unless you are towing a trailer. The trans will only shift into overdrive when it is needed.

Answer 3

Early manual automotive transmissions were limited to three or sometimes four speeds, with only the most sophisticated being five speeds. This left an unfulfilled need for a higher gear ratio for highway cruising, which was filled by the addition of separate overdrive units. However, automotive manual transmissions manufactured since the 1980s tend to include a larger selection of gear ratios than before, the highest of which is usually greater than 1:1. This trend has rendered overdrives a complex and obsolete solution to economy gearing in automobiles, and very few cars are fitted with them today, although they still appear on large trucks, where more gear ratios are always in demand.

Unless you're driving a truck and pulling a load, leave it on

Answer 4

On a car overdrive is the tallest gear than can be used. For example: if you have a 5 speed automatic transmission overdrive would be the 4rth and 5th gears. It allows the engine to turn at the lowest RPM per mile driven. An automatic transmission also incorporates a lockup feature to hydraulically lock the torque convertor to the trans so there is no slip.

You can leave it on all the time. If the engine and trans are not going fast enough to make use of overdirve it will not engage.

All of these feature allow the trans and engine to operate efficiently for best gas mileage and lowest wear and tear.

Answer 5

Overdrive should NOT be used for normal, stop-and-go driving ( with old-fashioned, separate OD ). The gears, in older cars, anyway, will break and chip teeth eventually if you are trying to accelerate under load or hard shifting. It should only be used ( in cars older than mid-80's ) for highway driving for gas mileage reasons. Maybe modern cars with the OD option or a 5th gear aren't as bad, but with an older car, it is hard on the gear teeth to run in that mode. I don't think I'd give up the power and torque even in more modern cars by leaving it in OD, unless there is a computer managed override that lets it be used automatically. The older cars you had to kick it in manually, and it was effective across the full gear range, whereas the newer OD / 5th gear setup is strictly a 5th gear, i believe, and not as hard on the transmission. So it depends on how old your car is - check your Owners Manual for correct operational procedures. - The Gremlin Guy -