# rear end ratio



## wally (Apr 24, 2014)

I have a 1970 GTO four-speed m-20 safe-t-track what am i running


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## Matthew (Feb 11, 2011)

Wally, the easiest way to check your gear ratio is by counting the revolutions of the drive shaft on one complete turn of a rear wheel. Start by lifting the rear end of the car off the ground. Transmission needs to be in neutral. Put a piece of masking tape on the drive shaft and a piece of tape on one of the rear wheels. Turn the rear wheel one complete revolution and count the revolutions of the drive shaft. You will likely have a partial revolution at the end. You can estimate the balance of the revolution. As an example: if the you drive shaft turns three and a half, you most likely have a 3.55:1. Nearly four turns would likely be a 3.90:1 gear. Of course, you can always take the cover off and find the numbers on the ring gear. Example: 41 15 meaning you have 41 teeth on the ring and 15 on the pinion or a 2.73:1 gear ratio. Regards, Matt


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## Chris-Austria (Dec 23, 2010)

I think you should test it... mark the position of one rear wheel and the position of the driveshaft. Turn the wheel 10 times and count the rotations of the driveshaft. For example if the driveshaft turned 35.5 times after you turned the wheel 10 times you have a 3.55:1 rear end ratio.

Edit: I posted at the same time as Matthew. I like to turn it 10 times because you get a more accurate number.


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