gear - mph - rpm for 2015 6sp auto

[carplan15]

so I took some notes while driving and fiddling with the electronic shifter button

1 - 9 - 2000
2 - 14 - 2000
3 - 22 - 2000
4 - 30 - 2000
5 - 42 - 2000
6 - 58 - 2000

any math wizards here ? I have the 15" wheels there must be some way to relate these numbers to the rear differential ratio yes ?

 

[The Champ]

You don't have a rear differential in a FWD car...

Why not just look at the Chevy website and know for sure? It varies by engine, transmission and whether your car is an RS or not.

If you have a 1.8 with the automatic your final drive ratio is 3.47. If you have a 1.4L you have a 3.23, unless you have an RS. The RS will have a 3.53.

http://media.gm.com/media/us/en/chevrolet/vehicles/sonic/2015.tab1.html

Unless you have an RS that has 15" wheels, there is some discrepancies in your numbers. Just being 1 MPH off will affect the results.

15" OE tires are 24.9" tall. 5th gear is your 1 to 1 ratio for calculating gear ratio. You say the speed is 42 MPH.

Using a Summit's gear ratio calculator, those factors equate to a 3.54 final drive ratio.

Gear Ratio Calculator - Free Shipping on Orders Over $99 at Summit Racing

Now if your actual speed was 43 MPH, that calculates to 3.45 - which is very close to what a 1.8L auto would have. Based on 15" wheels - I'm thinking you have the 1.8L.

 

[carplan15]

a FWD car...

oops yes that's why asked for math wizards

thanks much good info in your post !

yes engine is 1.8l

 

[Maddmatts]

Or you could do the boring thing and look up the factory specs on GM Powertrain Products