gjimene2
07-26-2005, 06:35 PM
Your thread got closed, and just so that everyone will know. The difference in D's is that one is for drive and the other is for over-drive.
A little bit of history
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 deman
How it works
The overdrive consists of an electrically or hydraulically operated epicyclic gear train bolted behind the transmission unit. It can either transfer the input drive shaft directly to the output shaft, called a propshaft (1:1), or increase the propshaft speed so that it turns faster than the input shaft (1:1 + n). Thus the propshaft may be "overdriven" relative to the input shaft. It is actuated by a knob or button, often incorporated into the gearshift knob, and does not require operation of the clutch.
-Wikipedia (http://en.wikipedia.org/wiki/Overdrive_(mechanics))
Google is your best friend
A little bit of history
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 deman
How it works
The overdrive consists of an electrically or hydraulically operated epicyclic gear train bolted behind the transmission unit. It can either transfer the input drive shaft directly to the output shaft, called a propshaft (1:1), or increase the propshaft speed so that it turns faster than the input shaft (1:1 + n). Thus the propshaft may be "overdriven" relative to the input shaft. It is actuated by a knob or button, often incorporated into the gearshift knob, and does not require operation of the clutch.
-Wikipedia (http://en.wikipedia.org/wiki/Overdrive_(mechanics))
Google is your best friend