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Strength - There are four usable styles you can find in a junk yard. They range from light duty to extreme duty but in all cases the larger 31 spline axle versions are stronger than the 28 spline version of the same unit.
The 67-73 Mustang type is considered light duty uses both axles.
The 57-68 early passenger car and half-ton pickup rear end is considered a medium duty unit and came in both 28 and 31 spline axles.
The 70-79 Ranchero / Torino are considered a high performance unit again being produced with both 28 and 31 spline axles.
The 69-77 Galaxie / Lincoln and 73-86 half-ton pickup used both size axles and the 31 spline version should be considered the strongest available and can be used for extreme duty applications.
Width: all measurements are flange to flange
1957-59 Ford - 57 1/4"
60-64 Ford 59 1/2"
57-59 Ranchero and SW = 57 1/4"
1964-71 Full sized cars - 61"
1979-81 Lincoln Versailles - 58 1/2"
1972-79 Ford intermediate & Full Size - 63"
70-79 Ranchero / Torino = 63"
73-86 Pickup = 65"
57-72 half-ton pickup = 61 1/4"
73-86 half-ton pickup = 65 1/4"
66-77 Bronco = 58"
1977-86 Ford F-150, Bronco - 65 1/4"
1977-86 Ford E-150 - 69 1/4"
77-81 Granada / Versailles = 58 1/2"
67-70 Mustang / Cougar / Fairlane / Comet = 59 1/4"*
70-73 Mustang family = 61 1/4"*
69-77 Galaxie / Lincoln = information not given but in any case it will need to be narrowed for use in a street rod.
* Denotes a gray area involving some of the earlier part being found on 70 Model year cars. Note:After 1970 all axles were the 31 spline style big axles. For 28 spline units the last 4 inchs were machined downfor the 28 spline ends. If you shorten the axles more than 4 inches they are big enough to take 31 spline.

Conversion from 28 Spline to 31 Spline

To change the third member to 31 spline, the only parts needed are the differential side gears, they are available from Ford, about $20 apiece. The other part of the conversion is the carrier bearing size. There are two carrier bearing inside bore sizes, and two carrier bearing outside bore sizes. There are three possible combinations, small ID-small OD , large ID-small OD , and large ID-large OD. Factory 31 spline axles came with the last two bearing configurations, but not with the first. On 28 spline carriers, the axle bore on some of them are not large enough to allow the 31 spline axles to pass through. The carriers with the large ID bearings can be bored out to use the 31 spline axles. Not a precision job, just big enough for the axle to pass through, I use a cut off end from a 31 spline axle to check when it's large enough. I takes less than an hour to do both sides, and could be done at a vocational school by a novice. The small ID bearings won't have enough material left for reliability if bored out for 31 spline axles. Also if your housing has the small axle bearings, you will have to have axles custom made, as there are no factory axles with 31 splines,and small axle bearings. Both the large axle bearing, and the extra large axle bearing (some F150 trucks) had 31 spline factory applications. From about 1970 on, the big Fords, Mercury's, and Lincoln's has axles big enough to respline with 31 splines if they are shortened about 4" per side. Both 4 1/2" and 5" bolt patterns are available. If you want to redrill to a 4 3/4" Chevy bolt pattern, use truck axles, as there is more room for the new pattern without hitting the other holes. The drum pilot may have to be turned down, depending on the drum used. The Chevy drums of corresponding size to the ford brakes will fit if the pilot is turned down.

Converting manual adjusters to later model auto-adjuster brakes

Use Wagner #283 shoes, drilled for the self adjuster mechanism, use Wagner self adjuster kit F98370/1, and wagner Combikit F87351. That should supply all the parts you need. These parts are listed for a F100 with 11" by 1 3/4" brakes.

Pinions

Daytona Pinions first available on with 63-64 427 full size cars, and other rare ultra Hi-po cars.

Ford Carrier ID Tags

Below are 2 tables showing the codes from the tag on a ford rearend the code will tell you if it is a 8 or 9 inch and what ratio is supposed to be in the carrier