Rearend Swap info - FAQ


Aug 19, 2004
Opelika, AL
here is the information on Ford 9" rearends I have compiled...

All of the following has come from various sites:

These measurements are from flange to flange. Subtract 5" for bare housing length.

65-66 Mustang 57.25 inches
67-70 Mustang 59.25 inches
71-73 Mustang 61.25 inches
77-81 Versailles 58.50 inches
74 Maverick 8" 56.50 inches
75 Mustang II 8" 57.00 inches
67-73 Mustang, Torino, Ranchero, Fairlane 9" 59.25 inches to 61.25 inches
57-59 Ranchero and station wagon rears, 57.25 inches
66-77 Bronco 9", 58 inches
77-81 Granada/Versailles, 58 inches
67-71 Comet, Cougar, Mustang, Fairlane, 59.25 inches
71-73 Mustang, 61.25 inches
64 Falcon 58 inches
67 Cougar 60 inches
67 Fairlane 63.50 inches (coil springs)
72 Ford Van 3/4 ton 68 inches
73-86 65.25 inches
57-59 Ranchero and station wagon 57.25 iches (narrowest 9" housing)
66-77 Bronco 58 inches but has 5-on-5 1/2 inch diameter bolt circle
67-73 Torinos, Rancheros, Fairlanes 59.25 inches or 61.25 inches
67-71 Comets, Cougars, Fairlanes 59.25 inches

Where to find the 9" rear axle

67-73 medium and big block Mustangs and Cougars
66-71 Fairlanes, Torinos, Montegos, Comets, and other Ford intermediates
with big blocks
57-59 V8 Fords and Mercurys
77-81 Lincoln Versailles & Trucks

Type of 9" axle housings

67-73 Mustang/Cougar - light duty, thinnest housing material, small axle
bearings, 28 and 31 splines
57-68 passenger car and 1/2 ton truck - medium duty, stronger than Mustang
type, 28 and 31 splines
Ranchero/Torino - heavy duty thick wall housing, 3.25 inch diameter axle
tubes with flat tops
69-77 Galaxies (coils), Lincolns (coils), and late pickups (leaf)- 3.25
inch diameter all the way to the backing plate, coil housings have upper
control arm mount

How to recognize 9" housing centers

57 - no dimples, flat center band up the center of the rear cover, bottom
drain plug
58-59 - two dimples on back of housing, flat center band, some had drain holes
60-67 - two dimples, flat center band, oil level hole in back cover
63-77 Lincoln, LTD, Thunderbirds had 9.375 inch centers, housings were cut
away at the gasket surface for ring gear clearance, one curved rib at the front
top portion of differential. Strong, but no gears.

Types of 9" Axles

28 spline axles cannot be shortened and resplined (they're tapered)
Some can: 69-73 Mustang and Cougars have a straight 28 spline axle.
72 and earlier 31 spline axles have the ability to be shortened
73 and later 9" (big cars) have a 5-on-5 bolt circle and the axles cannot be
67-73 Mustang axles identified by wheel flange:
oval hole - 28 splines two large holes and counter sunk center - 31 splines

Various informative web sites:

Versailles Swap:
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57-59 Ranchero and station wagon 57.25 iches (narrowest 9" housing)

The 57-59' full size passenger car is more common than the Ranchero/wagon and also uses a 57.25" 9" rear, but has the small axle bearings similiar to a 65/66' Mustang. That allows the 65/66' 8" Mustang axles and bearings to swap right in. Mustang 8" backing plates and drums can be used without modification. Axle seals outer diameter are larger than the Mustang's so you must by seals listed for the 57-59'. This is the easiest rear to swap from a 8", especially if you want to use your old axles, bearings and brakes.

The Ranchero and Station Wagon have a larger flange bearing and, although the 65/66' Mustang axles are useable, larger diameter bearings must be installed. Larger backing plates and drums must be used so be prepared for some added expense.

The 57-59' rears require a 3" U-bolt and the appropriate spring perch. This is NOT a standard Mustang size (for any year) so be sure to get them from the donor car or modify your existing perch and get new 3" U-bolts from NAPA.

Original Mustang shocks and shackles can be used. You can also transfer the 8" brake line tubing and hose to the 9", but the Y block may end up about 4" from the original location. I simply tacked a nut there and ran an appropriate sized bolt through the block into the nut.

The 57-59' passenger car rears use a short yoke and a 1310 type U-joint. That allows you to reuse your original driveshaft and U-Joint. Not sure about the Ranchero/wagon yokes.

A hose made for a dual exhaust car (ie GT) will give you a long bracket that can be bent to clear dual exhaust.

You can upgrade a 57-59' rear to 31 spline axles if you change out the center section and add 9" axles (stock or aftermarket) designed for a 65/66' Mustang.
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All this information is very helpful for my reference and I am saving all of it, but never having experience with working with rear ends I am lost in information overload, hopefully someone will be kind enough to repeat it again for the slower classmates.
I recovered a 429 drive train with a 9" rear end from a '69 Mercury Marquis that I plan to install into my '69 Coupe. The wheel to wheel flange measures approx 65" and had the coil spring purches with the control arm mount and 3" dia yoke, I am not clear from the above comments if this doner rear end can be modified or not.
Additionally I would like to modify to a tractionlock with 3:55 gears.
Thanks in advance.
I would like to make a correction. The spline count cannot be reliably identified based on the center of the axle's wheel end. An oblong recess may denote 28 spline axles on an 8" rear, but the flat center with two holes does not necessarily indicate 31 spline axleson a 9". I have a 9" out of a late-50s car and it has 28 spline axles, but also a flat center like the alleged 31 splines.
i just installed a 78 mgranada rear end in my 65 and it fit perfect i just needed 67-68 shock mounting plates and u bolts. i also added new springs and bushings,and magnum 500's. now on to the front for upgrades.
Which Ford cars use 35 spline pinions?

Anyone know what rear ends use a 35 spline pinion/yoke?

I bought a complete Lincoln Versailles for my 66 fastback. It has Trac-Lok and so the only thing I'm planning on changing is the ring/pinion gears (to 4.11) and to get a yolk for u-joints. Currently, theres a flat-flange yoke that mounts to a driveshaft with a flat-flange instead of directly connecting to the u-joint.

I'd like to use the yolk from another rear end I have, which is a 69 Galaxy. This rear end is 31 splines on the axel, but I dont know how many splines are on the yoke. If it helps, the rear end has coil spring perches, ~63" wide, and had a WAR case.

If the galaxy rear end has 35 splines, could I order a pinion with 35 and put it in the versailles 3rd member?
I'm not sure what leads you to believe that the Galaxie pinion would be 35 spline. I also don't know exactly what the spline count on the pinion actually is. I do know that unless the Galaxie rear is some oddball non-Ford assembly, it's pinion yoke should swap right over onto the Versailles pinion.
Sorry - I need to pick up a book or something on rear ends...

Say I want to swap out a new rear end, like the ones you mentioned above. All the different flange widths, does that make a difference? Or will I only be able to swap one with the same width as the my stock one?

Thanks for the list, it is great! :D
I just put a 8.8 out of a 96 Explorer with rear disks in my 70. I had to move the spring perches but it wasn't to much trouble other than that.

Hi dude, new to this forum stuff... I have an explorer rear axle outside waiting to go under a 70 sportroof. I have no idea where to start. Any help or suggestions would be awesome... I have already ground off the perches and bought new ones to weld on. And I got the flange from spicer. What was your driveshaft length when finished? Sorry bout all the questions, I'll relax for now. Thanks
The Explorer 8.8s are popular for three reasons; leaf perches, disc brakes, and (usually) an LSD. The negative for using them is the off-center diff. Mustang 8.8s often have the LSD and disc brakes with a centered diff, but they did not use leafs which means even more cutting/welding.

Swapping either into a early Stang is not that hard and there have been many threads about that swap in the past.
im working on swapping an explorer 8.8 into my 66. i had it narrowed on one side and just comes out shorter than a stock 66 8" rear!!! LSD, discs, 31 spline axles, oh my!!! and uner $700 for the swap, ya!!!

Its still a work in progress though