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Ford 9" History - Identification

Ford used the axle from around the 1957 model year right up until the early 1980’s in cars and trucks.

Variations by Ford exist in the size of the outer axle bearings in the housings and carriers both, as well as with the spline count on the axle shafts. Generally most cars received the small axle bearings and 28 spline axle shafts. Exceptions to this were the ultra Hi performance Boss 302’s, Boss 429’s, 427’s, 428 CJ/SCJ and the 429 cars which received the 31 spline carriers and axle shafts. Some of the heavier cars like the Galaxies, later Tbirds and mid 70's Torinos also received the larger wheel bearing housings.The trucks varied more, early half ton trucks got the 28 spline axles and carriers, while sometime in the early 70’s the switch was made to mostly 31 spline axles and carriers for trucks while some vans remained 28 spline. Most of the later trucks also received the larger axle bearings housings. A small bearing housing can be differentiated from a large bearing housing by the size of the nuts and thread used to retain the brake backing plates to the housing, the small bearing housings use 9/16 socket size nuts with 3/8” fine thread, while the larger bearing use 3/4” socket size and 1/2” fine thread.Because many one half ton trucks continued to utilize the 9 inch (both 2 wheel & 4 wheel drives) right up until about 1982 these housings are by far the most abundant(*Note: Some 1/2 ton Vans and Trucks used the 9 inch right up until about 1985/86 or so in limited quantities*), and with many 1973 to 1979 pickups to still be found on the road and in junk yards. And since the “Limited slip” or Locking rear end (often referred to as a “POSI”) came to be a popular option starting in the early 1970’s, many of the units found today at car swap meets and shows are the units pulled from trucks with the 31 spline carriers with the
 “Traction Loc” style posi unit. The actual car posi units which were primarily 28 spline carriers can be much more difficult to locate since the supply is limited to the few cars and early Broncos (and some early trucks) which received them. When it comes down to actual shafts as well, since the truck lug pattern in most cases differed from the car, and due to the bearing size differences, 28 spline car axle shafts are much more abundant than car 31 spline axle shafts, and often aftermarket shafts have to be purchased if one wants to use a truck 31 spline carrier in a car.
The carrier case you see frequently is the C7AW-E, it is the one commonly found in the trucks, vans and cars throughout the late 60's and the 1970's, right up until around 1985 in some truck applications. It may have a higher nodular iron content and better casting than the earlier single ribbed cases it replaced and that is why it remained in use so long, and the double ribbed N case was no longer needed for passenger car/truck applications (this also coincided with the demise of most performance engine options in the 70’s).
Most carriers for sale at swap meets/ car shows are this C7AW-E case , they were pulled from trucks and cars from the 1970’s.
The earlier housings used in cars from 1957 to mid 1960’s tended to be the weakest and had abrupt ending butt welded carrier centers to tubes and a smooth backside. Later housings appeared in 1966 with the familiar “Hump” in the backside middle and stronger tubes.
The later truck housings received even beefier center carrier housings and tubes and this style of center carrier housing is best suited for drag cars or narrowed rear ends , due to the added strength in the middle (referred to as the "Banjo style").
Where To Find:

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" 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 available
Axle Widths:

65-66 Mustang 57.25 inches
67-70 Mustang 59.25 inches
71-73 Mustang 61.25 inches
77-81 Versailles 58.50 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