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Old 06-06-2007, 01:59 AM
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Default Gear ratios
What exactly is a gear ratio ? What does something like 3:79 or 4:11 or 4:33 mean ? I would really appreciate it if someone could explain it to me in a simple manner. Thanks
 
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Old 06-06-2007, 02:32 AM
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a gear ratio is the number of times the drive shaft turns to make the rear wheels turn.

example:

4:11 means the drive shaft turns 4.11 times to turn the rear wheels 1 time
 
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Old 06-06-2007, 05:50 AM
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Originally Posted by ceb
a gear ratio is the number of times the drive shaft turns to make the rear wheels turn.

example:

4:11 means the drive shaft turns 4.11 times to turn the rear wheels 1 time
Or is it that the drive shaft turns 4 times to turn the wheels 11 times?
 
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Old 06-06-2007, 09:11 AM
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Originally Posted by honestashol
Originally Posted by ceb
a gear ratio is the number of times the drive shaft turns to make the rear wheels turn.

example:

4:11 means the drive shaft turns 4.11 times to turn the rear wheels 1 time
Or is it that the drive shaft turns 4 times to turn the wheels 11 times?
Nope what Ceb said is correct.

4.11 is going to get worse fuel millage than a 3.29 but the 4.11 will have alot more pulling power anyone know why?
 
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Old 06-06-2007, 09:17 AM
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Originally Posted by Mack2
Originally Posted by honestashol
Originally Posted by ceb
a gear ratio is the number of times the drive shaft turns to make the rear wheels turn.

example:

4:11 means the drive shaft turns 4.11 times to turn the rear wheels 1 time
Or is it that the drive shaft turns 4 times to turn the wheels 11 times?
Nope what Ceb said is correct.

4.11 is going to get worse fuel millage than a 3.29 but the 4.11 will have alot more pulling power anyone know why?
Because it is spinning more times to move the rear wheels one time, it is creating more inertial energy and transferring that to the wheels. So the higher the ration, the more energy transferred to the wheels and subsequently the road, which equals more torque or pulling power. Simple physics.

Really though, that's just a wild blind guess!! :idea: But I think I'm on the right track.
 
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Old 06-06-2007, 10:50 AM
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Originally Posted by Mack2
4.11 is going to get worse fuel millage than a 3.29 but the 4.11 will have alot more pulling power anyone know why?
Not necessarily. It depends on all the variables. Different engines and HP ratings, transmissions, final drive ratio's, how it's driven, etc. 8) 8)
 
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Old 06-06-2007, 01:09 PM
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Default Re: Gear ratios
Originally Posted by Graymist
What exactly is a gear ratio ? What does something like 3:79 or 4:11 or 4:33 mean ? I would really appreciate it if someone could explain it to me in a simple manner. Thanks
http://www.howstuffworks.com/gears.htm
 
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Old 06-06-2007, 05:48 PM
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Originally Posted by driver67373
Originally Posted by Mack2
Originally Posted by honestashol
Originally Posted by ceb
a gear ratio is the number of times the drive shaft turns to make the rear wheels turn.

example:

4:11 means the drive shaft turns 4.11 times to turn the rear wheels 1 time
Or is it that the drive shaft turns 4 times to turn the wheels 11 times?
Nope what Ceb said is correct.

4.11 is going to get worse fuel millage than a 3.29 but the 4.11 will have alot more pulling power anyone know why?
Because it is spinning more times to move the rear wheels one time, it is creating more inertial energy and transferring that to the wheels. So the higher the ration, the more energy transferred to the wheels and subsequently the road, which equals more torque or pulling power. Simple physics.

Really though, that's just a wild blind guess!! :idea: But I think I'm on the right track.

Thanks guys. What can I say, I've got a NC education.
 
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Old 06-06-2007, 11:25 PM
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Many thanks for all your responses....they certainly gave me a much better idea about the issue. Cheers and drive safe everyone.
 
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Old 06-07-2007, 01:43 AM
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Originally Posted by driver67373
Originally Posted by Mack2
Originally Posted by honestashol
Originally Posted by ceb
a gear ratio is the number of times the drive shaft turns to make the rear wheels turn.

example:

4:11 means the drive shaft turns 4.11 times to turn the rear wheels 1 time
Or is it that the drive shaft turns 4 times to turn the wheels 11 times?
Nope what Ceb said is correct.

4.11 is going to get worse fuel millage than a 3.29 but the 4.11 will have alot more pulling power anyone know why?
Because it is spinning more times to move the rear wheels one time, it is creating more inertial energy and transferring that to the wheels. So the higher the ration, the more energy transferred to the wheels and subsequently the road, which equals more torque or pulling power. Simple physics.

Really though, that's just a wild blind guess!! :idea: But I think I'm on the right track.
Thats why heavy haulers usually have rear ends with numbers like 4:11, 4:30, 4:56, even 4.88 mated to 18 speed transmissions with overall reduction ratios around 20:1. Sometimes with extra brownie boxes with granny gears for even more reduction. When you're trying to move loads nearly twice the size of the average truck, you want a lot of low gearing.
 
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