O/D itu = Over Drive
Ini saya quote dari Om Wiki: Overdrive can refer to two different things. An overdrive is a device which was commonly used in automobiles <http://en.wikipedia.org/wiki/Automobiles> to allow the choice of an extra-high overall gear ratio <http://en.wikipedia.org/wiki/Gear_ratio> for high speed cruising, thus saving <http://en.wikipedia.org/wiki/Fuel_efficiency> fuel, at the cost of less torque <http://en.wikipedia.org/wiki/Torque> . Usually the final or 'top' gear is called overdrive. Non direct drive gears increase torque multiplication at the expense of higher engine rpm and thus, decreased fuel economy. It also refers to a combination of gearing inside a transmission <http://en.wikipedia.org/wiki/Transmission_%28mechanics%29> or transaxle <http://en.wikipedia.org/wiki/Transaxle> which results in the output speed being greater than the input speed. In the latter case, "overdrive" does not refer to a physically separate identifiable part/assembly. History Early manual automotive transmissions <http://en.wikipedia.org/wiki/Transmission_%28mechanics%29> 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 <http://en.wikipedia.org/wiki/Gear_ratio> than before, the highest of which is usually greater than 1:1. This trend has rendered the overdrive 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. Usage Generally speaking, overdrive (OD) is the highest gear in the transmission. Most automatic transmissions <http://en.wikipedia.org/wiki/Automatic_transmission> have three 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 achieve better fuel efficiency, and often quieter operation on the highway. When it is switched on, the transmission can shift into overdrive mode after a certain speed is reached (usually 70+ km/h [43+ mph <http://en.wikipedia.org/wiki/Miles_per_hour> ] 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 70 km/h (approx. 43 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 third gear when more load is present. When less load is present, it shifts back to OD. Under certain conditions, for example driving uphill, or towing a trailer, the transmission may "hunt" between OD and the third 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 <http://en.wikipedia.org/wiki/Engine_braking> braking is desired, for example when driving downhill. The vehicle's owner's manual will often contain information and suitable procedures regarding such situations, for each given vehicle. Overdrive was widely used in automobiles with manual transmission particularly in Europe (see below) and was commonly available on either top gear alone, or on top gear and the gear immediately below (eg third gear and fourth gear. In this case gear changing is still possible in all gears, even with overdrive disconnected. Overdrive simply adds effective ranges to the gears, thus overdrive third and fourth become in effect "third-and-a-half" and a fifth gear. In practice this can lead to an overlap of gears in the third/fourth and overdrive-third/overdrive-fourth ranges, providing greater flexibility particularly in performance cars. How an overdrive unit works The overdrive consists of an electrically or hydraulically operated epicyclic <http://en.wikipedia.org/wiki/Epicyclic_gearing> gear train bolted behind the transmission <http://en.wikipedia.org/wiki/Transmission_%28mechanics%29> unit. It can either couple the input driveshaft <http://en.wikipedia.org/wiki/Driveshaft> directly to the output shaft (or propeller <http://en.wikipedia.org/wiki/Propeller_shaft> 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 <http://en.wikipedia.org/wiki/Aisin_Seiki_Co.> , 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 <http://en.wikipedia.org/wiki/Clutch> . Newer vehicles have electronic overdrive in which the computer automatically adjusts to the conditions of power need and load. Semoga membantu ya om. J BRgds, Brave2000_AU ^-^ BH 1718 AK - Bandung ^-^ From: [email protected] [mailto:[email protected]] On Behalf Of Deni Lukmanul Hakim Sent: Thursday, January 08, 2009 3:56 PM To: [email protected] Subject: Re: [baleno] Baleno Next G Auto 2003 Mau back to the topic lagi ah :) Saya juga punya baleno matic 2002, tapi masih gak ngerti sebenernya fungsinya O/D itu apa ya? Apakah kalau di gigi rendah O/D-nya dimatikan saja, dan baru dinyalakan di gigi tinggi? Sudah googling tapi gak ketemu2.. Bahkan singkatan O/D saja tidak tahu :( Makasih yang udah mau bantu jawab.. [Non-text portions of this message have been removed]
