Gear ratio identification

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Jan 30, 2014 | 06:31 AM

okie72

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Gear ratio identification

I am going to look at a front and rear end the guy says they have 4:10 gears but no tags on them. My question is how many teeth should the ring gear have and how many should the pinion have so I can make a positive i.d. before I buy. Also they are out of a 78or 79 supercab f150. Did any half tons come out with 4:10 gears?

Jan 30, 2014 | 09:29 AM

fitzmotor

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The gears should have the ratio stamped on the ring gear, if not just mark the ring gear and the pinon, rotate the pinon 4.1 times and the ring gear should make 1 full revolution.

Jan 30, 2014 | 12:54 PM

okie72

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The last one I took apart did not have the ratio stamped on the ring gear it was smooth all the way around. Can you count the ring teeth and the pinion teeth and divide them?

Jan 30, 2014 | 12:58 PM

Filthy Beast

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From: Taxachusetts

Quote:

Originally Posted by okie72

The last one I took apart did not have the ratio stamped on the ring gear it was smooth all the way around. Can you count the ring teeth and the pinion teeth and divide them?

Yup!....10 characters

Jan 30, 2014 | 01:07 PM

85e150

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Quote:

Originally Posted by okie72

The last one I took apart did not have the ratio stamped on the ring gear it was smooth all the way around. Can you count the ring teeth and the pinion teeth and divide them?

Count and divide is the way.

This here shows tooth counts for many ratios. 41/10 is your magic combo:

Richmond Gear Ford Ring & Pinion Sets - Free Shipping on All Orders @ JEGS

Helpful tips and info, fwiw:

Tech

Jan 30, 2014 | 02:08 PM

NumberDummy

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From: Simi Valley, CA

AXLE code stamped on the Warranty Plate, located on the left door face below the latch.

Jan 30, 2014 | 09:02 PM

okie72

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Thanks for the info guys this helps a lot!

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Feb 2, 2014 | 09:46 AM

tabascom16

More Turbo

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From: Salisbury, PA

The easy way to do it:

Put the transmission in neutral and jack one tire off the ground.

Rotate the wheel one revolution and count how many revolutions the driveshaft makes. Driveshaft rotation is HALF of the gear ratio.

About 1 3/4 turns - 3.55
About 2 turns - 4.11
About 2 1/4 - 4.56

Never trust tags as over the years someone could have changed the gears and put the tag back on anyways.