How To Find The Gear Ratio

There is always a good amount of math involved in every project, and sometimes it can be a little daunting. Thankfully when it comes to finding your car's gear ratio, it's a lot easier than you think. All you need is some tape and a marker!

[korykimbrell]

This works for a positraction. On a "one wheel peel" or open rear end. You have to turn the wheel twice

[smigletat]

“There is a mathematical equation”...We’re just not gonna give you that exact equation! Lol

[jamicl]

I've done this years ago. Those were good times. 😎

[tomtee]

Or open differential cover to check gear oil and change. Write down numbers on ring gear most stock gears will have something like 41 10 = 4.11

[ThatOneGuySometime]

Spin the tire ten times. Use a zip tie around the drive shaft with a long tail as a “flag”. By spinning the tire ten times, you would see the shaft spin 35.5 times in this instance. That way you get a MUCH more accurate reading.

[danielbrealey]

It's simpler to do this the other way around. Mark tyres and driveshaft and then count how many turns of the driveshaft it takes to get one rotation of the wheels

[xodzphone]

"one revolution of the engine", whatever that is

[scottsolfermoser]

For an open differential you have to turn both Wheels evenly

[trentmckenzie]

I had a 1997 Nissan pickup truck with 5-speed manual, 4x4. The little 2.4 was doing 3200rpm just to go 65. I quickly sold that vehicle as I knew this would wear everything more quickly and give me diminishing returns.

I miss that truck.

[RadDadisRad]

I have a spread sheet that all I need to do is input my tire size, final drive, transmission gear ratios and engine rpm.

[joshuadavis]

You can just pull the specs off the internet easily. Unless it’s been damaged or modified in some way you should have no trouble finding the gear ratios.

[urdel_durdel]

Final drive ratios on all rwd cars I've seen is cast somewhere on the diff itself

[victorvictor]

By the way big tires makes difference so make sure you install the right tire before you touch the differential thank you

[eribertoacedo]

Turbo 400 gear ratio is 1 to 1. In third gear !

[slackwayneo]

Is it a position or a non?Posse rear you need to know that first

[FactConspiracy]

Theoretical top speed. Final drive, final trans gear, engine rpm and tire diameter. Only way to figuring top speed without actually trying it.

[jadenvoshall]

Do a 6.9 idi build for towing and do a pull with it

[charlesgrieve]

MPH × Gear Ratio × 336 ÷ Tyre Dia = RPM

[geoffreymills]

It's called the Spicer gear calculator, look it up, , , and no ish

[perrylankford]

Roll the tire 10 revolutions and you get the EXACT gear ratio.