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Enjoy these easy to use flash gadgets for determining final drive ratio, ring and pinion ratio and Saginaw 3 speed identification and gear ratios.
Automotive enthusiasts, as well as professional racers, determine the magic numbers quick and easy with these tools!
Dirt Track Race Car Setup Technical Data
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Ring and Pinion Gear Ratio Calculator

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How to calculate Ring & Pinion Gear ratio with the rear end in the car.

Jack up the rear axle and support it with jack stands. Put the transmission in neutral and then rotate the rear drive shaft by hand. While turning, count the number of drive shaft revolutions required for one revolution of the tire. If the drive shaft turns approximately 3-3/4 times, you have a 3.73 ratio, etc. It may help to use a piece of chalk mark a reference point on both the tire and drive shaft. For increased accuracy it is recommended to rotate the wheels two times and divide the result by two. You may have different gearing front to rear (but the difference is typically very slight) so be sure to check the other axle too.
Number of Turns Approximate Gear Ratio
2 - 3/4 2.72:1 or 2.77:1
3 - 0 3.07:1
3 - 1/2 3.54:1
3 - 3/4 3.73:1
4 - 0 4.10:1
4 - 1/2 4.56:1
4 - 3/4 4.88:1

1969 Chevrolet Camaro Trivia
The 9561 package featured the all iron 427 L-72 with an 780-cfm carburetor, hi-rise manifold, rectangular port heads and forged steel crank.
The L-72 produced about 95% percent of the power of ZL-1, but only added $489.00 to the base cost of the car. If coming equipped with the
4-speed transmission the engine came with solid lifters and produced 425hp. When equipped with the automatic transmission hyraulic lifters were used.
Final Drive Gear Ratio Calculator

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Saginaw Transmission Identification and Ratio


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 Power Glide Transmission
Used from 1970 to 1972. This is a 2 speed automatic. It was available on the 6 cylinder and 307 V8. Powerglides were manufactured with 2 different low gear ratios. 1.82 and 1.76
This transmission is strong, or at least can be made strong, and it's
popular with people who drag race cars
and circle track racers.

TIP: The low gear ratio can be determined by the length of the input shaft.


Powerglide Low Gear Ratio
Measure the overall length of the input shaft to determine the low gear ratio. (Stand transmission up with the point straight up to remove shaft.)
There is a small bronze thrust washer inside the transmission that the end of the input shaft rests against. Make sure it stays centered before inserting the input shaft back into the transmission. Do not force and lightly lubricate.
12 5/8 inches long 1.82
12 7/8 inches long 1.76


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