**How To Figure Gear Ratios** – We use cookies to do better. By using our website, you agree to our cookie policy. Cookie settings

A “wiki” similar to Wikipedia, meaning many of our articles are co-authored by multiple authors. To produce this article, 34 people, some anonymous, worked to edit and improve it over time.

## How To Figure Gear Ratios

Mark an article as reader approved when it receives enough positive feedback. This article received 64 testimonials and 84% of readers who voted found it helpful , it gets our readers’ approval status

#### Derivation Of Willis Equation (fundamental Equation Of Planetary Gears)

In mechanical engineering, gear ratio is a direct measure of the ratio of the rotational speeds of two or more interlocking gears. As a general rule, when working with two gears, if the drive gear (receiving torque directly from the engine, motor, etc.) is larger than the driven gear, the next gear will rotate faster and vice versa. We can express the basic idea with the formula Gear Ratio = T2 / T1, where T1 is the number of teeth on the first tool and T2 is the number of teeth on the second.

A “wiki” similar to Wikipedia, meaning many of our articles are co-authored by multiple authors. To produce this article, 34 people, some anonymous, worked to edit and improve it over time. This article has been viewed 1,682,133 times.

To determine the gear ratio of a gear train with 2 gears, start by determining your gears. The gear connected to the motor shaft is considered the first gear or “drive gear” and the other gear, which has teeth connected to the drive gear, is considered the second gear or “drive gear”. Calculate the number of teeth on the drive gear and on the driven gear. Then, divide the number of teeth on the drive gear by the number of teeth on the drive gear to get the gear ratio. For example, if the drive gear has 20 teeth and the driven gear has 30 teeth, the gear ratio is 1.5. If you want to learn how to use gear ratios to calculate gear speeds, keep reading! You just bought your latest hot rod, but in true car style, you think an upgrade is in order. You have decided that rearend gear exchange is the first place you want to go. Before deciding whether an upgrade is in order, don’t you think you should first find out the rear gear ratio of your car?

## How To Find Out The Axle Ratio On A Ford Pickup

How to determine the gear ratio on the bottom of a car is a question I am often asked. I am surprised by the frequency of the question, because finding the answer is a really simple task. While you can pull off the back cover and find the ratio number on the ring gear, there is an easier way. In fact, it only requires you to have a floor jack and a pair of jackstands. To help you make identifying gear easier, I’ve decided to put together a little outline of how to find out exactly what gear you have without opening the back.

If you are unsure of your results when using the wheel rotation method, the number of teeth is stamped on the ring gear. The smaller number is the number of pinion-gear teeth. The larger number is the tooth count of the ring. To find the gear ratio, divide the larger number by the smaller number. In the example above, 37 ÷ 12 = 3.083333. These are 3.08 gears.

Knowing your rear gear ratio is important when you’re considering a transmission upgrade, adjusting your transmission speedometer, selecting a torque converter, or getting professional help with camshaft selection.

### Calculating Gear Ratios For An Orrery. An Orrery Is A

Before you start determining the gear ratios, you also need to know if the rear end is a “posi” or open differential. This is necessary because the gear ratio setting is slightly different for each unit.

To begin with, raise the rear of the vehicle with jacks on the floor and place a good jack under the vehicle on the frame or rear stand. Once supported, place the transmission in center and turn one of the rear wheels. If the opposite wheel turns in the same direction, then you have a posi-or limit-slip-differential. If this is the case, you can leave both jackstands under the car. If you rotate one of the rear wheels and rotate the other in the opposite direction, you have an open differential. In this case, you need to remove one of the jackstands and place a tire on the ground.

Soapstone marks the plate and “A” in rubber letters is used as a symbol.

### Transmission Ratios Of Planetary Gears (willis Equation)

When doing this test, some people like to use soapstone or chalk to mark the tires and driveshaft to make it easier to count all the revolutions. Modeler’s color markers also work well if you want to do this. I usually focus on the symbols supplied by the specific tire (ie the specific letter in the tire name) and use one of the simple brackets and that as my reference. If using a paint marker, make a large, visible dot on both the inside of the tire and the inside of the driveshaft.

When you apply your sign, if the car has a posi unit, both tires will be in the air. Make one rotation of the marked tire while counting the number of times the axle has moved. Let’s say your driveshaft makes 3 3/4 turns, which would set the gear ratio to 3.73. If you get about 2 3/4 revolutions, you have a 2.76 gear ratio.

As mentioned earlier, if your car has an open differential (not positive), you will need to test with a rear wheel. Again, mark the inside of the tire and the driveshaft mounting points with your colored marker. Now, rotate the suspended tires

#### Willis Equation For Planetary Gears

History and count the number of driveshaft turns. The reason for the two rotations is that the opening actually rotates half as many times as the posi due to the design of the “open” operation. Again, if the driveshaft rotates 3 3/4 turns to rotate the two tires, you have a gear of 3.73. The driveshaft which rotates 2 3/4 times has a declared gear ratio of 2.76.

Hopefully, this short tutorial will provide some knowledge that every motorist should know and make decisions about the dreaded short gear shift.

Create a custom newsletter with your favorite content straight to your inbox from Chevy Hardcore, absolutely FREE!

#### Calculate Gear Ratio (without Calculator)

We promise not to use your email address for anything other than exclusive updates from the Power Automedia network. This gear ratio calculator determines the mechanical advantage of installing two gears in an engine. Gear ratio tells us how much speed the output gear will increase or decrease or how much torque is lost or gained in the system. We install this calculator with gear ratio equation and gear reduction equation, so you can quickly determine your gear ratio.

Continue reading to learn more about calculating gear ratios and how they are essential in building simple machines (and even complex machines).

Prefer to watch rather than read? Learn all you need in 90 seconds with this video we made for you:

#### What Is A Gear Stage?

A gear is a wheel with teeth that can change the direction, torque, and speed of the rotational motion applied to it. Gears come in a variety of shapes and sizes (although the most common is the involute gear – see involute function calculator), and these differences explain the translational or rotational displacement. Gear shifting occurs when two or more gears in the system mesh together while in motion. We call this gear system a gear train.

In a gear train, turning one gear turns another gear. The gear that receives the primary force, either from the driven motor or simply the hand (or foot in the case of a bicycle), is called the input gear. We can also call it the driving gear because it initiates the movement of all other gears in the gear train. The last tool that the input tool affects is called the output tool. In a two-gear system, we can call these gears the driving gear and driven gear respectively.

The motion of the output gear may be in the same direction as the input gear, but it may be in a different direction or axis of rotation depending on the type of gear in gear up training. To help you visualize this, here are examples of different types of gears and their input-output gear relationships:

## Frequencies Of A Gear Assembly

Gear ratio is the ratio of input gear circumference to output gear diameter. In gear training. Gear ratios help us determine the number of teeth for each gear. Desired output speed / angular speed, or torque (see torque calculation).

We count the tools