1978 Ford F100 rear axle ratio - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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post #1 of 3 (permalink) Old 06-30-2015, 01:42 PM Thread Starter
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1978 Ford F100 rear axle ratio

Hi everyone, I want to find out what my diff ratio is on my pickup. What I could get from the rear axle assembly is the following: 9E21 C5AW 4668A 22 DIF
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post #2 of 3 (permalink) Old 06-30-2015, 04:33 PM
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Re: 1978 Ford F100 rear axle ratio

Welcome to the forums. You found the casting number for the pinion support. Unfortunately, that doesn't tell us much. I would first check two other places - on the driver's door edge is the warranty tag of plastic-covered paper. If still there, it should list a code for "axle", and two if it's 4x4. If that's gone or obliterated, look for a metal tag (about 1/2" x 1-1/2") under one of the bolts holding the gear case into the rear axle housing. It lists the info including gear ratio. Post what you can find here, and then we can tell you how to confirm the info, in-case the gears have been changed in the last 37 years.


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post #3 of 3 (permalink) Old 10-23-2015, 12:13 PM
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Re: 1978 Ford F100 rear axle ratio

9E21 is the date code E-May 21-DAy 9- Year C5AW IS THE CASTING # ITS Been a long but hope this helps.
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