There are ways to determine your gearratio without having to open up yourdifferential. The differential, alsocalled a pumpkin, is a mess if youopen it up. The gear oil stinky, it takesa lot of time, andyou want toavoid opening it up, it if at all possible. But there aresome places that you can check andthings that you can do to determine yourgear ratio without having to go there.
Check Window Sticker (Monroney)
The first place to check is really easy.It’s most likely in your glovebox, oryour paperwork when you bought yourvehicle. It’s the window sticker, alsocalled a Monroney. If you have a buildsheet (if you had a custom-built from themanufacturer), you’ll also find it there.
Asyou can see right here, this stock 2005F-150 hada 3.55 ratio limited-slip. Now I’ve changed it to 4.56 butthat’s how it started its life.
Check Differential Cover
Now if thatdoesn’t pan out, there’s two other placesthat you can check… on the axle and thedifferential cover itself.
On the axleyou might have a sticker, and on thedifferential cover you might have alittle metal tag that’s sticking out.That will have the gear ratio stampedright on that.
Do a Driveshaft Turn Test
Ifyou’re still notgetting anywhere, jack up the rear end of your vehicle and mark your wheel and thedriveshaft. I just used some blue tape. Turn your wheel one time. While you’re turning it one time, count thenumber of rotations on your drive shaft.That will determine your gear ratio.
In my case it rotated about four and ahalf times and my gear ratio is 4.56, soI know this test works spot-on.
Check Ring Gear Stamping
So you’re still not getting anywhere?Well, guess what? You’re going to have tocrack that differential on open becauseyou’re going to need to get to the ringgear and possibly take a look at thepinion gear as well.
If you can get tothe ring gear, turn your wheel until youcan see the stamping on the side of it.You’ll see the number of teeth. That’sthe number of teeth for the ring gear andthe pinion gear.
Calculate Ring & PinionTeeth
You can’t find the stamping on the ring gear?Start counting! Count all the teeth onthe pinion gear and the ring gear. Once you have those two numbers, dividethe number of teeth that are on the ringgear by the number of teeth that are onthe pinion gearand BAM–you have your gear ratio!
Where Else To Look
Heremy last few bits of advice. First, if it’sa new vehicledon’t go ask your salesman. He’s notgoing to know these technical detailsand if he does give you an answer,it’s probably the wrong one… so justdon’t even bother.
The other one is tocheck online forums for an answer. You might find somebody else thatjust bought that vehicle and they havethe exact same question and they havethe answer already. But, your vehicle might stillbe different.
The best thing to do isto use all those techniques and lookat all those places that I just showedyou and you’ll be able to determine the gear ratio for your vehicle.
If you have any other advice, please leave it in the comments section, below.
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Summary
How To Determine Your Gear Ratio
Description
How to determine your gear ratio without having to open up your differential.
Chris Duke
Chris Duke
FAQs
Count all the teeth on the pinion gear and the ring gear. Once you have those two numbers, divide the number of teeth that are on the ring gear by the number of teeth that are on the pinion gear and BAM–you have your gear ratio!
How to determine gear ratio? ›
The calculation uses the number of teeth in the ring gear and divides it by the number of teeth in the pinion gear to provide you with a “[result] to 1” ratio. For example, if the pinion gear has 41 teeth, and the ring gear has 11 teeth, the ratio would be calculated as 41/11, which is equal to 3.73 = 3.73:1.
What is the formula for calculating gear ratio? ›
Students derive the formula for finding the gear ratio of a pair of gears: gear ratio = teeth in driven gear/teeth in driver gear.
What is the gear ratio in Quizlet? ›
Gear ratio is expressed this way to compare the number of TEETH the input and output have. Ratio = # teeth in the output (driven) gear / # of teeth in the input (drive) gear.
How to calculate gear ratio in PDF? ›
It provides the equation to calculate gear ratio as the number of teeth on the input gear divided by the number of teeth on the output gear. In the example given, the input gear has 24 teeth and the output gear has 48 teeth, so the gear ratio is 0.5 or 1:2 based on the number of teeth.
How to calculate ratio? ›
If you are comparing one data point (A) to another data point (B), your formula would be A/B. This means you are dividing information A by information B. For example, if A is five and B is 10, your ratio will be 5/10. Solve the equation. Divide data A by data B to find your ratio.
How to find gear ratio by VIN? ›
You don't. That information is not contained in the VIN, UNLESS a specific model only gets one rear end ratio. VIN tells country of manufacture, vehicle make, class, engine type, size, date of manufacture, plant and serial number. That is the ONLY information contained by the VIN.
What is the formula for gearing ratio? ›
How to Calculate the Net Gearing Ratio. Net gearing can also be calculated by dividing the total debt by the total shareholders' equity. The ratio, expressed as a percentage, reflects the amount of existing equity that would be required to pay off all outstanding debts.
How to calculate gear ratio with RPM? ›
T1*S1=S2*T2 where, T1=number of teeth on the driver gear, S1= angular speed on the driver gear, T2=number of teeth on the driven gear and S2=angular speed on the driven gear. 38 teeth*360rpm=T2*144rpm.
Why do we calculate gear ratio? ›
Gear ratio calculation involves determining the ratio of the rotational speeds or torques between two intermeshing gears. It helps in understanding the relationship between the sizes and number of teeth on the gears, allowing engineers to design systems with desired speed or torque requirements.
To calculate the gear ratio:
Divide the number of driven gear teeth by the number of drive gear teeth. In our example, it's 28/21 or 4 : 3. This gear ratio shows that the smaller driver gear must turn 1,3 times to get the larger driven gear to make one complete turn.
What is the basic of gear ratio? ›
The gear ratio is calculated by dividing the angular or rotational speed of the output shaft by the angular speed of the input shaft. It can also be calculated by dividing the total driving gear's teeth by the total driven gear's teeth.
Which of the following is used to calculate gear ratio? ›
The gear ratio is calculated by dividing the output speed by the input speed (i= Ws/ We) or by dividing the number of teeth of the driving gear by the number of teeth of the driven gear (i= Ze/ Zs).
How to find the gear ratio? ›
Calculate Ring & Pinion Teeth
Count all the teeth on the pinion gear and the ring gear. Once you have those two numbers, divide the number of teeth that are on the ring gear by the number of teeth that are on the pinion gear and BAM–you have your gear ratio!
What is the formula for gear ratio speed calculator? ›
The gear ratio is also the factor by which the input speed is multiplied to deliver the output speed. For example, a two-gear system featuring an input gear with 10 teeth and an output gear with 20 teeth would have a gear ratio of 10 / 20 = 0.5 10/20 = 0.5 10/20=0.5, or 0.5 : 1 0.5:1 0.5:1.
What is the formula for gear ratio efficiency? ›
A: The calculation for gear ratio is simple: divide the number of teeth on the driven gear (or output gear) by the number of teeth on the driving gear (or input gear). This can be represented by the gear ratio formula: Gear Ratio (GR) = Number of Teeth on Driven Gear (T2) / Number of Teeth on Driving Gear (T1).
How do you calculate gear ratio from speed? ›
Speed (MPH) = (RPM × Tire Diameter (inches) × Overdrive Gear Ratio) / (Gear Ratio × 336)
- RPM is the revolutions per minute of the engine.
- Tire Diameter is the diameter of the tire in mm.
- Overdrive Gear Ratio and Gear Ratio affect how the engine's power is translated to movement.
