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Old 09-30-2002, 12:06 PM
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modro modro is offline
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Default How do you Determine Gear Ratio?

How do you determine the gear ratio on a rearend?

I have an 8 3/4 Sure-Grip (thought it was open, now know it is a Dana Power-Lok SG) Third Member, and I want to determine the ratio on it.

I imagine it could be done via just counting the teeth on the R/P gears, but in order to do so, I need the tooth counts on the different gear ratios. I want to drop this rearend into my Newport since it has an open diff in it, but I want to find out the ratio on it. If it turns out to be something like a 3.55+, I'll just drop it in the RR instead, and drop the RR rearend (also sure-grip) into the Chrysler.
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Old 09-30-2002, 12:25 PM
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Default Tooth Count

You don't need to know all the possibilities....Only what you have in your 3rd member. Lay it up on the bench. Mark the ring gear with a small daub of paint on one tooth and count all the teeth from there. Do the same with the pinion. Divide the number of ring teeth by the number of pinion teeth and you have your ratio.

As an example, my Dana 60 has 46 teeth on the ring and 13 on the pinion and 46/13 = 3.54 rounded. This ain't rocket science.
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Old 09-30-2002, 12:48 PM
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Default

If you have the 3rd member out, just rotate the ring gear. The gear ratio is stamped on the side of the ring gear.
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Old 09-30-2002, 02:54 PM
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Simple enough.

I feel retarded now, because I should have thought to divide the numbers.

Stupidity leak

It is out, so checking the side is of no problem.
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Old 09-30-2002, 02:58 PM
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3.91 gears

Thx

It was stamped right on the side, just had to clean some oil/gunk off to see it.
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