Gear ratio's

nhkid28 · January 22, 2003

If you have a truck that came from the factory with 245-75-16 tire and 3.73 gears are the gears the same as a truck that came from the factory with 265-75-16 and 3.73 gears? If they are and same wouldnt the truck with the 265's actually have a gears more like 3.60. How does that work? If you started with 245's and went to 285's your gear ratio would be around 3.46. On the other hand if you started with 265's and went to 285's your ration would be 3.59.

I guess my question is, are the gears that go into each truck are different depending on what size the tire is?

asepgrad98 · January 22, 2003

if you got bigger tires you just go futher for each rev

DeezBlueZ · January 22, 2003

No, ring and pinion gears( the actual ratio of the ring to pinion) are the same for different tire sizes. Smaller or larger diameter tires will change your effective or overall gear ratio as you mentioned accordingly.

nhkid28 · January 22, 2003

ok, then if you have a truck with 265's from the factory you will have the same overall ratio as a truck with 245's from the factory that switched to 265's. Correct?

asepgrad98 · January 22, 2003

Shaners · January 23, 2003

The rear gear ratio (for example we'll say 3.73), means that for every 1 revolution a wheel makes the driveshaft will turn 3.73 revolutions. When you go to a larger sized tire, then you change the "effective" gear ratio. Although you will still have a 3.73 rear gear, when you go to a larger diameter of tire it will make the truck "feel" like the "effective" ratio is more like a 3.46.

The rear gear ratio is always a constant (in GM's 3.42, 3.73 or 4.10).