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Old 03-06-07, 08:49AM   #1
Corey
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Default gear size question

Is there a way to find the gear size in my rearend on my firebird with out tearing it down. Stock 67
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Old 03-06-07, 11:13AM   #2
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put the rear of the car on jackstands and with the trans in neutral hold one tire from turning(providing it's an open rear) and put a mark on the other tire and a mark on the yoke on the rear or driveshaft. Now count the turns the driveshaft til the mark on the tire you made makes a complete rotation around. AN EXAPLE: If you can turn the driveshaft 2 and 3/4 of a turn the gear ratio is most likely 2:78. For a posi rear where both tires spin the same direction when you turn the driveshaft you wont have to hold a tire from spinning.
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Old 03-06-07, 12:31PM   #3
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Gear ratio or gear size? The above for gear ratio and gear size (actual inches) can usually be figured out by the diff. cover shape or a tag on the diff.
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Old 03-06-07, 10:56PM   #4
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I was looking for size i.e. 10" or 9". The tags gone. but thanks for the ratio formula.
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Old 03-06-07, 11:01PM   #5
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http://www.drivetrain.com/gmdanadiffgaskets.jpg
http://www.powertrax.com/diff.htm
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'74 Ventura, '74 455 (9.5 comp), KRE D ports 305cfm (SD performance), Scat, Ross, SD Road Paver solid roller, TII, 850DP (shaker455) , 1-3/4 hookers, dual 3'' Pypes/3'' Magnaflows, TH350, conti 10'' 3800, 3.73 , ET Streets 28x13.5x15.

Have not run with the KRE heads yet, excited to hopefully give it a go this summer!!
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Old 03-07-07, 11:21AM   #6
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Whats on the tag doesnt mean thats what gear is in there, people do gear swaps and like to leave that tag on for some reason.
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Old 02-28-16, 05:12AM   #7
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If it's gear size you want , it will be 8.2 rear gears in your 67 bird. As for ratio you will have to pull the diff cover & count the ring gear & the pinion gear & divide the pinion by the ring & that will give you your ratio.
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Old 02-28-16, 12:16PM   #8
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Quote:
Originally Posted by Mb125 View Post
put the rear of the car on jackstands and with the trans in neutral hold one tire from turning(providing it's an open rear) and put a mark on the other tire and a mark on the yoke on the rear or driveshaft. Now count the turns the driveshaft til the mark on the tire you made makes a complete rotation around. AN EXAPLE: If you can turn the driveshaft 2 and 3/4 of a turn the gear ratio is most likely 2:78. For a posi rear where both tires spin the same direction when you turn the driveshaft you wont have to hold a tire from spinning.
THIS^^^^^ Unless you need a fluid change you don't need to pull the cover.
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