Easiest Way to Determine Rear End Gear Ratio on a Open Differential

In this episode of Budget Build Garage Nick explains and demonstrates the easiest way to determine rear end gear ratio on a open differential. The best part about the video is that Nick shows how to calculate your rear gear ratio without taking anything apart.
For this video we're determining gear ratio on a rear end of the 1969 Ford Mustang. This Ford Mustang has an 8.8 inch rear end with a 2.73 ratio. Using the method in this video will enable you ti determine the rear end gear ratio of any open differential vehicle.

[BudgetBuildGarage]

Thanks for watching everyone. What is your favorite way to determine rear end gear ratio?

[raygordon]

Everything you're doing is correct. But all you have to do on an open diff is spin it once and multiply the yoke spins by 2. Never heard of the 10 times way. Ford only has so many rations in 8 and 9 inch so you'll be in the ballpark ratio wise. My Mustang was taching at freeway speeds, jacked it up, locked the other wheel, turned wheel once while watching the yoke, yoke went around twice. Times that by 2 = 4.11

[Rhawk]

Thank YOU! I was able to find out I have 3.07s in my Chevelle.

[Winterstick]

Instead of chalking the other tire, just don't raise it.

[msharp]

Not sure why you would spin it 10 times. More work than needed. Just spin it twice and count the driveshaft turns, and it will give you the same results.

[paulgutiereziii]

Cool, had to verify my rock crawlers gears 10 rotations 26.5 x 2 = 53 . I have a 5.28 gear ratio on my Toyota.

[mandojr]

Do I have to lift both tires completely off the ground and chock one side or can I just lift one side up since mine is open differential.

[BretBunton]

I’m putting an ls3 with a tsp cam, lifters, valve springs, push rods with a tr6060 xl 6 speed manual in my 65 chevelle. What gears should I go with? I don’t need to go over 95 in an old car. Should I just go with 4:10?

[LastBastian]

Thanks! This was helpful. ... except for the part where you suggest googling Chevy gear ratios because "there's only like twelve of them" ...I googled, and they list like a hundred of them so.... ?

[cutetweety]

My corona 1966 1c diesel engine 5 spped gear, what is the reason that speed does not cross 135 km per hour, gear axel ratio is 2 and 1

[godofyota]

Does it matter which side you chalk on an open rear-end?

[greghenderson]

I got a even 13 with 10 spins my chevy 7.5 10 bolt non posi with 1 wheel spinning.

13 x 2 = 26...

My gear ratio is 2.6 ?

[AgentSmith]

Why did he spin it 10 times and the posi only once?

[viperram]

I have a 2019 Challenger Hellcat and the MSRP says 2.66:1, I was thinking of going with 3.70:1, what do you think it would change?

Also, is their a way to find out gears in a AWD?

[mgarc]

Why does a 4.11 ratio give better speed than a 2.73 or do I have that backwards. I've been known to do that from time to time. Dude, you have that ass backwards. Please explain. thanks.