What does overdrive do?

Question

My new car has overdrive. I'm clueless! What does this mean and what does it do? Does it use up more gas?

Thanks!

Answer 1

Overdrive is basically a 5th gear,it is use full when overtaking an other car,you turn the overdrive off and the car will change back a gear giving you more power and then turn it back on when you have overtaken so you go up a gear and the car does not rev as high saving petrol etc. Don't panic about it though, you can just leave it on and never change it if you like, a lot of people don"t know what they are for. Take care on the road.

Answer 2

Generally speaking, overdrive (OD) is the highest gear in the transmission. Most automatic transmissions have 3 speeds and overdrive (fourth speed). Overdrive allows the engine to operate at a lower rpm for a given road speed. This allows the vehicle to realize better fuel efficiency, and often quieter operation on the highway. When you switch it on, you allow the transmission to shift into overdrive mode after the certain speed is reached (usually 45+ mph (50–65 km/h}) depending on the load). When it is off, the transmission shifting is limited to the lower gears. For normal driving conditions, operation of the overdrive should be enabled only if the average speed is above 45 mph.

It may be necessary to switch it off if the vehicle is being operated in a mountainous area.

The automatic transmission automatically shifts from OD to 3rd gear when more load is present. When less load is present, it shifts back to OD. Under certain conditions, e.g: driving uphill or towing a trailer, the transmission may "hunt" between OD and 3rd gear, shifting back and forth. In this case, switching it off can help the transmission to 'decide'. It may also be advantageous to switch it off if engine braking is desired, for example, driving downhill. For more details, check your owner's manual.


[edit] How an overdrive unit works
The overdrive consists of an electrically or hydraulically operated epicyclic gear train bolted behind the transmission unit. It can either couple the input driveshaft directly to the output shaft (or propeller shaft) (1:1), or increase the output speed so that it turns faster than the input shaft (1:1 + n). Thus the output shaft may be "overdriven" relative to the input shaft. In newer transmissions, the overdrive speed(s) are typically as a result of combinations of planetary/epicyclic gearsets which are integrated in the transmission. In these cases, there is no separately identifiable "overdrive" unit. A number of such transmissions and transaxles are manufactured by Aisin, for use in vehicles produced by many different manufacturers. In older vehicles, it is sometimes actuated by a knob or button, often incorporated into the gearshift knob, and does not require operation of the clutch. Newer vehicles have electronic overdrive in which the computer automatically adjusts to the conditions of power need and load.
Hopes This Helps you.

Answer 3

If your overdrive is off the car will not go into 4th gear. This could be usefull for hauling heavy loads or mountainous driving. It should be left on for normal driving (assuming you can turn it off manually).

Answer 4

youe overdrive is for when you are going over 65m.p.h. it is so you don't burn out your transmission. And no it doesn't use more gas you can drive in overdrive all the time if you want it doesn't hurt anything.

Answer 5

O/D allows your engine to spin at a slower speed at cruising speed, which SAVES gas. Around town, in slower traffic, it doesn't engage. If it DID, the engine would run TOO slow.