72 rear end swaps

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Nov 18, 2019 | 10:37 PM

Crystalc

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Joined: Nov 2019

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72 rear end swaps

Need some info/help with swapping out the rear end on a 72 f100. It had a 9 in 31 spline that's gone out and has to be replaced. I've had three brought out, but all have been about 4" to wide to fit the shackles correctly. I've seen that it can be replaced with ones from a mustang, Mercury, or Lincoln. But I don't know what years to look for to swap it out with or if there would be other modification that would have to be completed. So any help would be greatly appreciated!

Nov 18, 2019 | 11:58 PM

NumberDummy

Ford Parts Specialist

Joined: Nov 2006

Posts: 88,826

Likes: 787

From: Simi Valley, CA

Quote:

Originally Posted by Crystalc

Need some info/help with swapping out the rear end on a 72 f100. It had a 9 in 31 spline that's gone out and has to be replaced.

I've had three brought out, but all have been about 4" * too wide to fit the shackles correctly.

I've seen that it can be replaced with ones from a

Mustang...No Mercury...No or Lincoln...No.

Car rear axles will not work in a truck, it may be possible to swap the 3rd member, but you have to know beforehand how many splines the axle shafts have.

Car axle shafts are right and left specific, F100 axle shafts are the same right/left.

I need the following to discover what rear axle your truck has:

Rear axle ID tag located at approx 5 o'clock under one of the bolts that retain the 3rd member (pumpkin) to the housing.

AXLE code stamped on the 2nd line-far right of the Warranty Plate, riveted to the left door face below the latch.

The rear axle tag may be missing, but the Warranty Plate should still be there. Post the codes.

31 splines: More than likely your truck has a 9" rear axle with a 9 3/8" ring gear and Traction-Lock, rear axle capacity is 3600 lbs.

Most 1970/72 F100's have a 9" rear axle with 28 spline axle shafts and a 3,300 lbs. capacity rear axle.

*1973: Ford increased the width between the inner frame rails behind the cab to 37 1/2." 1961/72 F100's have 33 1/2" rear frame rails.

Nov 19, 2019 | 07:31 AM

john jamieson

Cargo Master

Joined: Jul 2015

Posts: 2,069

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From: tucson

Is there a reason it can't be rebuilt by a drive train shop? I would think it could be completely rebuilt for around $1500. No guarantees on a used axle.