I believe I have a 7 1/4 nonSureGrip rearend. I ve heard many ways to check gear ratio. Is this a correct method.
Jack up one rear wheel and mark with chock at bottom and mark driveshaft also at bottom. Count turns of the driveshaft to one turn of the wheel and multiply by 2.

Correct procedure for open rear axle (or worn-out Sure Grip) is Here. With working Sure Grip, you jack up BOTH wheels rather than just one.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I know with mine, I didn't think it had the little metal tag on one of the cover bolts with the gerar ratio until I did a thorough job of cleaning the rear end. The tag magically appeared after a good cleaning and the tag read "3.21".

As Doc pointed out to me a couple or 3 months ago, on a 7.25 the rato is stamped on the cast webbing of the differential ceter section, on the passenger side IIRC. Mine was 3.23.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Last night I counted the times my driveshaft turned to one wheel turning. To my amazement, the ratio was 1.75 driveshaft to 1 wheel. Dan, am I looking at a 2:23 ratio? Seems to be mighty high for a Dodge truck with a A833OD.

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85' D100
225cid
A833OD

Dan any way you can make you're 'determining rear ratio' a sticky as this question comes up all the time??????????

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

With an open differential, you must either (1) rotate the tire/wheel two turns, or (2) rotate the wheel/tire one turn and multiply driveshaft turns by two.

With 1-3/4 turns for one wheel rotation, it sounds like you have 3.55:1 gears (which IIRC, you have a truck, is not all that uncommon). 1-3/4 x 2 = 3.5

More accuracy can be obtained by rotating the wheel numerous times. e.g Rotate the wheel 10 times, and divide driveshaft rotations by 5.

-S/6

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The "Silver Bullet"
87 Ram D150