Rear Axle Codes

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Dec 27, 1999 | 11:21 PM

F100

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Rear Axle Codes

I have a 1982 F-100, 300 Six, C6 tranny. The door jam label gives an axle code of "015." Can anyone tell me what my gear ratio is, what type of rear axle I have, and, since I do not have a tach, what RPMs I am turning at 70mph. I'm concerned about engine health at that speed since I use my truck mainly on the highway. Is it safe to drive that speed with the setup up I have?

Dec 28, 1999 | 12:28 AM

Superdave

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Rear Axle Codes

According to my Chilton axle code:15 is a 3.25 ratio for 80-82 Fords. If your rear end does not have a removable cover on the back of it then its a 9" Ford rearend.

Dec 28, 1999 | 12:35 AM

Superdave

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From: Indiana

Rear Axle Codes

Dec 28, 1999 | 07:06 AM

Tall Paul

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Rear Axle Codes

Easiest thing would be to get a tach. I picked up a Sun mini-tach for $32. For tranny ratios, I had to call several dealers until I found one helpful enough to actually go look up the ratios for my '95s 5spd manual (most were too busy). Also I had the Helm Inc. shop specifications book for my 1984 and it gave all the truck tranny ratios. If you try to calculate the RPM from tranny and axle ratios, you have to consider that the wheel/tire radius is reduced a bit because it sits pressing on the pavement (this made about a 1500 rpm difference at highway speed in my calculations).