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

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.

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)

Re: Gear ratios
 

Thanks guys. What can I say, I've got a NC education.

Many thanks for all your responses....they certainly gave me a much better idea about the issue. Cheers and drive safe everyone.

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.