third member swap

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Apr 13, 2007 | 05:01 PM

todd jo

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Joined: Mar 2007

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third member swap

Can anybody tell me if a 9" third member from from a 76 pickup fit into a 9" housing in my 66 pickup? If the third members do not readily swap over, will the R and P?

I have a friend who has a higher gearset in a already pulled third member. I would like to put into my truck to turn down the RPMs at cruise sped. If there are differences is it obvious once the two are side by side? Dont want to cause problems by using incompatible parts!

Thanks, Todd

Apr 13, 2007 | 05:35 PM

acheda

Elder User

Joined: Feb 2004

Posts: 909

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From: San Luis Obispo, CA

From '57 on up 9" third members are interchangeable so far as fitting the banjo housing. The other issue is the number of splines on the axles. Most were 28-spline, but some were 31-spline, and aftermarket parts go even bigger. Just pull one axle from your truck and see if it fits the side gear splines in your buddy's third member. Look at the axle lengths and bearing diameters while you are at it - you might be able to swap axles too.

P.S.: R&P's will swap if the axles are different, but it is a lot of work. It might be easier to swap out the side gears or the differential housing. This would save a lot of the setup time.

Apr 13, 2007 | 07:37 PM

Pickupmanx2

Lead Driver

Joined: Jun 2006

Posts: 5,638

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From: Near Yosemite CA

Odd's are that it will fit, I have changed numerous ones out and have not run into any spline count troubles,,,,as of yet! Now I will,,,, but the majority were 28 spline

Apr 13, 2007 | 07:51 PM

NumberDummy

Ford Parts Specialist

Joined: Nov 2006

Posts: 88,826

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From: Simi Valley, CA

First 31 Spline rear axles = 1968

Standard equipment on 1968/72 F100 Camper Specials, optional on the others.