<font face="Verdana, Arial" size="2">Originally posted by wallstreet123456:
COuld someone please explain to me what this ratio talk means in plain english. I would like to understand this.
Gear ratios in a transmission simply discribe the speed difference between the power input shaft of the tranny (driven by the engine) and the power output shaft (drives the wheels). For example, if first gear is a 10:1 ratio, the engine will have to turn the input side of the transmission 10 turns to get 1 turn at the output side.
It gets a little confusing at first because the higher the number (20:1 as apposed to 10:1) the "lower" the gearing. A higher gear ratio will have a smaller number (5:1 is a higher gear ratio than 10:1) etc.
That's why they start with relatively low gear ratios (higher numbers) for first gear because that multiplies the power of the engine making it easier to get the car moving. Once it's moving, the amount of power needed to hold speed is much lower so they can go to a higher gear (lower numbers) so the engine doesn't need to spin as fast to perform the work. That equates to better gas mileage (usually) and a more relaxed ride because the engine isn't spinning up close to red line all the time.
In Albaby's post above, he lists the '01 and earlier Ody's gear ratios as:
1st = 2.534:1 (I know he didn't say the ":1" part but that's considered to be understood)
Anyway, it means the engine is turning 2.534 revolutions for every 1 turn of the output side of the tranny.
2nd = 1.502:1
3rd = 0.947:1 Here it gets a litte interesting. You've no doubt heard some of us refer to "overdrive (OD)". In this case, 3rd gear is a mild overdrive gear. It means that the engine is actually turning slower than the output shaft of the transmission.
4th = 0.605:1 This is a pretty healthy overdrive gear ratio. It's one of the main reasons the Ody EPA's at 25 mpg on the highway. The engine is only turning just over .6 revolutions for every 1 full turn of the output side of the tranmission. While it's great for mileage, it's lousy for performance but then again, we can't have it all!
Final drive = 3.941 This is the equivilent of the rear differential of a rear wheel drive car. It's where the power from the output side of the transmission is turned and sent to the drive wheels.
Now having said all of that, one of the big advantages the '02 Ody should enjoy over it's older sibblings is that, with the 5 speed transmission, they can run a lower first gear (higher numerically) which will allow the van to launch from a standing start with a lot more snap. Second, third and fourth gears can be spaced closer together to keep the engine in the heart of it's power band and thus keep the performance strong. Then they'll have that 5th gear overdrive so the engine can loaf along at highway speeds and keep the EPA fuel mileage on up where we'd like it to be.
I hope all this makes sense!