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-   -   how to tell what gear ratio in a 64 chevy 12 bolt (

klassickarman 08-22-2012 12:33 PM

how to tell what gear ratio in a 64 chevy 12 bolt
how do tell what gear ratio is in a 64 chevy 12 bolt rearend

big gear head 08-22-2012 01:21 PM

Must be a truck because the car 12 bolt didn't come out until '65. Remove the cover and count the teeth on the ring gear and the pinion gear. Divide the number on the ring gear by the number on the pinion gear. 41/11=3.73 Probably needs an oil change anyway.

klassickarman 08-22-2012 03:20 PM

Thanks gear head, I tried by getting all the numbers off the rear axle and that didn't work. So I did that and came out with 3.73.

RWENUTS 08-22-2012 03:22 PM

Jack up one wheel. Rotate it one revolution and count number of times driveshaft rotates. Multiply times 2 equals your ratio.

big gear head 08-22-2012 03:39 PM

If this is a truck 12 bolt with 3.73 gears then you also have a 4 series differential. I don't know what you have planned, but that is something that you will need to know if you are going to do a gear swap.

klassickarman 08-22-2012 04:02 PM

Nothing to fancy...just restoring it back to original. Just wantin it to have good highway gears.i pulled a 307 out of it and putting a 283 in it.

big gear head 08-22-2012 05:29 PM

If you are planning on going to something like a 3.42 or 3.07 gear then you will need a 3 series differential. Those gears won't fit the 4 series that you have now.

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