What is my gear ratio?

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Dec 14, 2003 | 06:31 PM

millwood1

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What is my gear ratio?

Can anyone help me out here? I have an 87 F150 and I want to find out what gear ratio the rear end has. The axle code on the inside of the door reads a 19. The tag on the rear end cover reads s814p 5588 7e04. I would like to know if it is an 8.8 rear end and what the fear ratio is. Any help would be appreciated.

Dec 14, 2003 | 06:45 PM

Fordlover55

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From: Kalispell, Mt.

I'm not sure what the "fear ratio" is, but here's an easy way to find out fairly close. Jack the rear end up, mark a spot on the tire and the drive shaft. Have someone turn the tire one exact revolution and while they do that, count how many times the drive shaft makes a complete revolution. For example... if the tire turns once and the drive shaft turns 3 and 1/2 times, you have a 3.50 gearing. If the drive shaft turns more or less, you can reasonably guess. I'm not sure what gear ratios automatics use, but they used to have 2.80 gears at one time.

Sometimes you can find the gear ratio listed inside the door on the plate there..depending on the year of the vehicle. Hope this helps some. Oh..and the 8.8...I assume you are wondering about the size of the ring gear. It may be an 8.5" but not sure. Ford hasn't made the "bulletproof" 9" rear end in years. Real big mistake, too.

Last edited by Fordlover1951; Dec 14, 2003 at 06:47 PM.

Dec 14, 2003 | 06:57 PM

fordeverpower

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From: iowa

i am sure it is a 8.8 inch rearend but i don't know the axle codes.

Dec 14, 2003 | 07:21 PM

StrangeRanger

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From: Copley, OH

19 is a 3.55:1 open rear
The second line of that tag should read "3 5588" meaning 3.55: ratio 8.8" rear end. Perhaps the 3 got taken out by the anchor bolt, it sometimes happens.

Dec 14, 2003 | 07:35 PM

acerockola77

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From: WA

3.55 ratio, 8.8'' rear.

Dec 15, 2003 | 05:03 PM

millwood1

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I appreaciate the help folks. The info is quite helpfull. I have another question though. Should I find a rear end from a 4 wheel drive around the same model or does anyone know off the top of your head if any other model w/ a 9 inch would work w/out having to have it cut down or anything like that?

Dec 16, 2003 | 04:09 PM

gatesj

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From: Remsen, NY

You probably want an 8.8 3.55, open or trac-lock (codes 19 or H9). I can't imagine it would make a difference if it was out of a 4x2 or 4x4. The '87 probably has ABS and you have to work some tricks to get the brakes to work with a 9", IIRC and you have to cut down or lengthen the driveshaft. Axle codes are at: https://www.ford-trucks.com/articles/axlechart.php.