How to figure out gear ratio of a rear end

I have the following information from the Chevrolet VIN Decoder. For example if we divide a ring gear with 41 teeth by a pinion gear with 10 teeth we find that.

For instance if the drive shaft rotates three and a quarter turns to one tire rotation then your rear axle gear ratio is 3251.

How to figure out gear ratio of a rear end. FIGURING REAREND GEAR RATIO Ring Pinion FORMULA. Engine RPM Cruise Tire Revolutions Per Mile Rear-end Gear Ratio EXAMPLE Without Overdrive. 1800 RPM 65693811 2731 EXAMPLE Without Overdrive.

2000 RPM 65693811 3041. EXAMPLE With Overdrive 30. 1800 RPM 65693811 2731 x 130 3541.

Count the number of revolutions the drive shaft turns using the masking tape attached to it as a guide to one tire revolution. For instance if the drive shaft rotates three and a quarter turns to one tire rotation then your rear axle gear ratio is 3251. Remove the masking tape from the drive shaft and tire.

Differential Gear Ratio Calculator. Enter the number of teeth on your ring and pinion gear set to find the gear ratio. Ring Gear Pinion Gear Ratio.

To find the ideal gear ratio for cruising use your RPM at peak Torque. If your max Torque is at 3300 RPM use 3300 for the RPM. Calculate Rear End Gear Ratio needed.

The number of driveshaft rotations will help you determine your rear axle ratio. For example if it turned 3 and a half times its a 3501 ratio. If it turned 4 and a quarter times its a 4251 ratio.

For better accuracy turn the wheel 20 times and divide by 2 for your rear axle ratio. If you are unsure whether you have a Posi Rear or not. If it takes about 2 and three-quarters turns its around a 273 gear ratio.

If its a little more than 3 you have 308s. If it takes about 3 and a quarter turns of the driveshaft you have 323 or 325 gears. Part 4 of 5.

Determining a more accurate gear ratio. This is the most accurate method of determining your gear ratio. Most gear ratios are not exact numbers making the spinning method less accurate.

Place the oil catch pan under the rear differential cover. Remove the bolts that hold the rear differential cover on. Select the value you want to solve for.

For the Tire field enter your tire diameter in inches. If you know your gear ratio then this doubles as a Vehicle Speed Calculator Just type in your info press calculate and youll get the right gear ratio without the guesswork. Another way to easily calculate gear ratio is multiplying 12 by your new tire size for example 1238456.

You may also calculate rear axle gear ratio by dividing pinion gear tooth count by ring gear tooth count. Tire specifications have a three number format 27575R16. Step 1 Find the VIN of your vehicle.

It can be found on the sticker on the inside of the drivers side door or on a stamped metal plate embedded in the dashboard above the steering wheel. It also is on your vehicles title. Axle ratio or rear end gear ratio is calculated by dividing the number of teeth on the ring gear by the number of teeth on the pinion gear.

Most differentials nowadays will have a sticker on the outside with axle ratio information. If you have a 342 rear end ratio and need more towing power you would switch to a 410 ratio. If you have installed larger tires they rob performance and you would want to go to a lower ratio like a 456 or 488 depending upon your tire diameter.

Want to search for rear end parts by application ask the Gear Wizzard. You should be able to find your gear ratio listed on the axle tag however if that has gone missing you can simply count the number of teeth on each gear and divide the number of ring gear teeth by the number of pinion gear teeth. Ring Gear Teeth Pinion Gear Teeth 41 11 373.

By simply dividing the ring gear tooth count by the pinion gear tooth count the ratio is determined. For example if we divide a ring gear with 41 teeth by a pinion gear with 10 teeth we find that. In the end its easy to see that mistakes in gearing can craft a truck load of trouble.

The real key to optimum performance is to take the engine torque curve the transmission gear ratios rear axle ratio and tire diameters into consideration as a total package. I have the following information from the Chevrolet VIN Decoder. Im trying to figure out which number determines my gear ratio.

Im assuming it is 342 or does the min or max number represent the ratio. This is from the decoder. Axle Ratio 1 - Rear 342 373 323 323 min 373 max Other transmission info from decoder.

To verify or to see if that ratio has changed you can jack up the rear axle and support it with jack stands. With the transmission in neutral rotate the rear driveshaft by hand. Count the number of driveshaft revolutions required for one revolution of the tire.

If the driveshaft turns approximately 3-12 times you have a 354 ratio etc.