# How To Figure Out Gear Ratios

How To Figure Out Gear Ratios – There are ways to set your gear ratio without opening your differential. The difference, also known as pumpkin, is a mess if you open it. Gear oil is smelly, it takes a long time, and if possible, you want to avoid opening it. But there are some places you can check and find out your gear ratio without going there.

The first place to check is really easy. It’s probably in your glove box, or in your paperwork when you bought your car. This is a window sticker, also known as Monroney. If you have a build sheet (if you had a custom build from the manufacturer), you’ll find it there too.

## How To Figure Out Gear Ratios

As you can see here, this stock 2005 F-150 had a limited slip ratio of 3.55. Now I have changed it to 4.56 but it started its life like this.

#### Gear Ratio Chart

Now if that doesn’t pan out, there are two other places you can look… at Excel and Differential Cover.

On the axle you may have a sticker, and on the differential cover you may have a small metal tag attached. It will have the gear ratio printed correctly.

If you still haven’t gotten anywhere, jack up the rear end of your car and mark your wheels and drive shaft. I just used some blue tape. Spin your wheel once. When you spin it once, count the number of revolutions on your drive shaft. This will determine your gear ratio.

## Spur Gear Calculator Hub

In my case it turns about four and a half times and my gear ratio is 4.56, so I know this test is working well.

So are you getting anywhere yet? Well, guess what? You need to open this differential because you need to get to the ring gear and possibly take a look at the pinion gear as well.

If you reach a ring gear, turn your wheel until you see a stamp next to it. You will see the number of teeth. This is the number of teeth for the ring gear and pinion gear.

### Vin Number And Gear Ratio

Can’t find a ticket on Ring Gear? Start counting! Count all the teeth on the pinion gear and ring gear. Once you have these two numbers, divide the number of teeth on the ring gear by the number of teeth on the pinion gear and BAM – you have your gear ratio!

Here are my last few pieces of advice. First, if it’s a new car, ask your dealer. He doesn’t know these technical details and if he answers you, it’s probably wrong… so don’t panic.

Another is to check online forums for answers. You may find someone else who has bought this car and has the same question and they already have the answer. However, your vehicle may still be different.

## What Is Rear End Gear Ratio And How Is It Calculated?

The best thing to do is to use all these techniques and check all the places I show you and you will be able to determine the gear ratio of your car.

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## Bigger Tires? Here’s What You Need To Know About Re Gearing

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#### How To Determine Your Gear Ratio

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## Single Speed Gearing

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### Gear Inch Calculator Chart

Located in the vibrant town of Ronkonkoma, an hour off the busy streets of New York City, GT Transmission is a great example of family values, dedication and craftsmanship… October 2014 Pit Stop, you explain so the horsepower and torque always runs at 5,252 rpm. And in the past you’ve published formulas for the relationship between miles per hour (mph), axle ratio, engine revolutions per minute (rpm), and tire size. But where does the constant “336” in this equation come from?

Vehicle speed (mph), engine speed (rpm), tire diameter (inches), trans gear ratio, and rear axle gear ratio are all interconnected. If you know four out of five of these values, you can determine what the unknown value is (or what is needed to achieve your desired goals). But to do this you must convert different units of measurement to a common value: revolutions per minute to revolutions per hour, and miles to inches. There is also a conversion of rotary motion (crank, gear and axle shafts) to rotational motion at the tire/ground contact patch, so you must factor in the diameter and circumference of the tire.

The unchanged formula for finding a vehicle’s mph involves multiplying the engine rpm by the number of minutes per hour (60) and multiplying the tire diameter by pi () to find the tire circumference in inches. Then multiply these two individual products together, and divide the total gear ratio times the number of inches in a mile (63, 360). “336” is simply the reduced, rounded integer value of these various constant values. See the red box for the invariant equation and how it is “reduced” to the constant “336” we use every day.

Unlike other versions of this formula you may have seen, I now include the trans gear ratio as a factor. Previously, most transmissions were 1:1 in high gear, but today’s transmissions have higher gears, so you need to factor that in as well. This allows you to solve for each trans gear, not just the top gear – which is useful for determining the best gear ratio spread.

If you need to run multiple scenarios to mix in a combo that meets your performance goals, I recommend keeping the formulas in a spreadsheet or programmable calculator. There’s another option that harkens back to the “BC” (pre-computer/pre-calculator) days: the old-school analog (aka “hand-operated”) rectangular, slide rule-like, force/acceleration calculator. doers Moroso still offers one of the most comprehensive, as shown in the images below. There are also wheel variations that we call “dream wheels”. This style is still available from Alexandria (PN RATIOCOMP). In a more modern vein, Summit Racing has an online gear ratio calculator. We use cookies for customization. By using our site, you agree to our cookie policy. Cookie settings

This article was co-authored by Grace Emson, MA. Grace Emson is a math teacher with over 40 years of teaching experience. Grace is currently an instructor of mathematics at the City College of San Francisco and was previously in the mathematics department at St. Louis University. She has taught mathematics at the elementary, middle, high school, and college levels. She holds an MA in Education with a specialization in Administration and Supervision from Saint Louis University.