How do i identify the rear diff gear ratio?
Elder User
Joined: Mar 2005
Posts: 878
Likes: 0
From: Cornelius, Oregon
Well the sure fire way, if you have the rear cover off is to count the teeth on the ring gear and the pinion gear. Then devide the ring gear tooth count by the pinion gear tooth count and that will give you the ratio. Not all (actually not many at all) are stamped with numbers. Sometimes you'll find a tag on the diff cover that says the gear ratio, but they often get lost or are simply not there, or may even be incorrect. Counting the teeth is about the only way to know for sure.
Post Fiend
Joined: Jul 2005
Posts: 8,462
Likes: 4
From: Durant, OK (SOSU)
If you don't want to break into the diff for the "right" way, check the VIN, tag on the door, and look for a tag on the diff. They probably will all line up and be correct with each other, then spin the tires and look to see if it looks like it matches the number everything else suggested.
Though Pit and Mil1ion are right, that's the only way to REALLY do it.
OR, you can get your tire diameter, tranny ratios, and calculate it using one of those online calculators.
Though Pit and Mil1ion are right, that's the only way to REALLY do it.
OR, you can get your tire diameter, tranny ratios, and calculate it using one of those online calculators.
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Posting Guru
Joined: Jan 2006
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From: Malvern, Ohio
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Posting Legend
Joined: Sep 2001
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This post contains a very accurate way of determining the ratio without counting teeth. It is from the FAQ thread in the 73-9 forum:
https://www.ford-trucks.com/forums/s...8&postcount=20
https://www.ford-trucks.com/forums/s...8&postcount=20
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