Gears / ratios

[bottomshot]

I'm trying to learn more about cars in general lately and one thing I'm looking at is gears and ratios. I see a lot of talk and suggestions on here regarding what gears to get but I don't understand enough to follow it. What does a bigger ratio mean, i.e. 4.10 compared to 4.55 in terms of power? Do they really have that much effect? How hard are they to switch out?

 

[4x4junkie]

4.10:1 means the input to the differential (pinion gear) turns 4.10 times for one rotation of the tires (ring gear). 4.56:1 means 4.56 rotations for one tire rotation, and so on.

The bigger the number, the "easier" it is for the engine to turn the wheels.
If you put big tires on your truck, it then becomes "harder" for the engine to turn them efficiently due to the tire's larger diameter (the tires roll at a slower RPM for a given speed), so you change the ratio to compensate for it (bringing the engine back to a more efficient RPM).

That help?

 

[adsm08]

Gearing is one of the primary determinants of how much power you have available, and what kind of fuel mileage you get. The higher the number the the more power you have at take off, but you loose top end speed and economy. If you want to put bigger tires on your truck then you need lower gears (higher numbers) in the rear end.

The right gears can make or break a car. If you want a good economy daily driver, 4.10 are probably a bad choice for gears, 3.45 or 3.73s would be a much better choice. If you want a rock crawler with 35s 4.10 or 4.55s would be much better than the 3.45s.

Swapping out rear end gears is not a job for an amateur. Its by far not the hardest thing to do on a vehicle, but it does take a fair amount of skill and a good knowledge of cars. Start by doing some little stuff first. Spark plugs, a clutch job, etc.

 

[bottomshot]

Thanks guys, great info!

 

[daniel3507]

Swapping out rear end gears is not a job for an amateur. Its by far not the hardest thing to do on a vehicle, but it does take a fair amount of skill and a good knowledge of cars. Start by doing some little stuff first. Spark plugs, a clutch job, etc.

I think it is a lot more precise than what a lot of people think though. It isnt just tossing a ring and pinion in there.

 

[adsm08]

I think it is a lot more precise than what a lot of people think though. It isnt just tossing a ring and pinion in there.

Oh I know. I've built a handful of diffs in the last few years.

The easiest to work with is the 9 inch because it has screw adjustments instead of selective shims.