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jimfulco · 06-17-2007, 11:20 PM

I wouldn't trust a code or a glove box ratio on a 27-year-old truck.

13.9 turns to 10 turns = 1.39 turns per turn

Multiply x 2 since one wheel was on the ground, and you get 2.78. The closest factory ratio to that was 2.73, so that's probably what you have.

To be absolutely sure, pop the cover off and look at the edge of the ring gear. There should be a 7-digit part number, and four 2-digit numbers, two of which are a date code, and two of which are the tooth counts of the ring & pinion gears. Divide the big one by the little one and that's your ratio.

06-17-2007, 11:20 PM	#8
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	Re: axle ratio 80 GMC I wouldn't trust a code or a glove box ratio on a 27-year-old truck. 13.9 turns to 10 turns = 1.39 turns per turn Multiply x 2 since one wheel was on the ground, and you get 2.78. The closest factory ratio to that was 2.73, so that's probably what you have. To be absolutely sure, pop the cover off and look at the edge of the ring gear. There should be a 7-digit part number, and four 2-digit numbers, two of which are a date code, and two of which are the tooth counts of the ring & pinion gears. Divide the big one by the little one and that's your ratio.