Ford Differentials. Joseph Palazzolo

9⅜-inch axle can typically be found on 1961 to about 1972 larger cars, such as the Lincolns and LTDs, and the high-powered pickup trucks from about the mid 1960s to the mid 1970s. These axles had large carrier bearings with an outside diameter of 3.265 inches. Some of these use the unique 3.250-inch outside-diameter wheel end bearings as compared to the typical large bearings, which are 3.150 inches. These axles are still not as strong as nodular iron 9-inch axles. There is no aftermarket support for these axles, so there’s no reason to buy one for a high-performance or racing application. Therefore, the only reason to use one of these is for a concours-type restoration for originality.

      There are no performance upgrades so you are stuck with used parts or, if you are lucky, new old stock. As a result, I highly recommend that you avoid this axle for any performance application buildups. You will be better off in the long run.

      But there is one good side to this axle; you can swap the third member with a 9-inch unit and retain the rest. So if your vehicle already has this housing and you want to upgrade the gears and differential, you have choices. You can even put the larger 9⅜-inch third member in a 9-inch housing but you need to machine some additional ring gear clearance in the axle housing. The bolt pattern for the third member is common between the two axle housings. I am not sure why you would ever want to do that but it is physically possible.

Part Numbers

      I could not review the history and identification of these axles without talking about the Ford part numbering system. The Ford part numbering system is well organized and structured as compared to some other original equipment manufacturers’ systems that just utilize the “next number in sequence” philosophy.

      Ford part numbers typically have three components: the prefix (three or four alpha-numeric characters) then a dash, followed by the basic number, another dash, and then the suffix or revision version. In some situations, there is even a pre-prefix with a single or double digit to help provide further clarification of the part’s history.

      Let’s look at the part number for the nodular third member that I referenced earlier as an example:

      C4AW-4025-B

      The first character is for the decade and the second digit is the year of that specific decade. The second digit is also for the year of introduction or year of last revision.

      All of the above holds true until the year 1999. It appears with the Y2K scare and other factors, Ford decided to revamp its date code strategy. Parts released in 1999 and forward follow this format:

      The third character is for the vehicle model code. For example, R3 is Mustang, H7 is F-Series Short Cab, L3 is F150/250. So a 2011 Mustang axle is part number BR3W-4001-KH.

       Ford Part Number First Character

       (8.8- & 9-Inch Axle ID)

First Character	Decade
A	1940 (often omitted)
B	1950
C	1960
D	1970
E	1980
F	1990

       This is a year-of-manufacture table for differentials. The first character is the decade, from 1940 to 1990, while the second is the year in that decade. So our example (C4AW-4025-B) was introduced in 1964.

       Ford Part Number Third Character

       (8.8- & 9-Inch Axle ID)

Third Digit	Model & Year
A	Ford/Galaxie (1958 on)
B	Bronco (1970–73), Maverick (1975–77), Fairmount (1978–83)
C	Remanufactured Parts (1966–75), Elite (1975), Capri (1979 on)
D	Falcon (1960–69), Maverick (1970–74), Granada (1975–83), LTD (1983 on)
E	Chassis Cab Truck (1970–73), Pinto (1976–80), Escort (1981 on)
F	Export sales, Trans Am Racing
G	Comet (1961–67), Montego (1968–76), EXP (1982 on)
H	High Performance Part, Medium and Heavy Truck (1966 on)
I	Not used
J	Marine and Industrial Engines
K	Edsel (1958–60), Comet (1975–77), Zephyr (1978–83), Marquis (1983 on)
L	Lincoln (1958–60), Mark (1961 on)
M	Mercury (1958 on)
N	Tractor (1958 on)
O	Fairlane (1962–68), Torino (1969–76), LTDII (1977–79), LN7 (1982–83)
P	Autolite and 1962 on, Motorcraft Brand
Q	Not used
R	Rotunda Tools (1962–69), Ford of Europe (1970 on), Remanufactured parts (1976 on)
S	Thunderbird (1958 on)
T	Truck (1958–65), Light and Medium Truck (1966–82), Bronco (1966–70, 73–82), Light Truck and Full–Size Bronco (1983 on)
U	Econoline and Club Wagon Van (1961–81)
V	Lincoln Continental (1961–81)
W	Cougar (1967–80, 83 on), XR7 (1981–82)
X	Truck (1970–73)
Y	Meteor in Canada (1962–72), Bobcat (1975–80), Lynx (1981 on)
Z	Mustang (1964–73), Mustang II (1974–78), Mustang (1979 on)
1	Not used
2	Pinto (1972–75)
3	Tempo (1984 on)
4	Comet (1971–74), Monarch (1975–80), Cougar (1981–82), Marquis (1983 on)
5	RVs (1974–75), Continential (1982 on)
6	Pantera (1971–75), Topaz (1984 on)
7	Courier (1971–85), Ranger, Bronco II (1983 on), Explorer (1991 on)
8	Capri (1972–75)
9	Turbine Engine Parts (1970–75)

       The third character in our example (C4AW-4025-B) is an A, which indicates it is from a Ford vehicle, specifically a Galaxie from 1958 or newer.

       Ford Part Number Fourth Character

       (8.8- & 9-Inch Axle ID)

Fourth Digit	Design Engineering Office
A	Light Truck Engineering Division
B	Body and Electrical Product Division
C	Chassis
D	Overseas Product Engineering
E	Engine North America
F	Electronics Division
G	Engine Merkenich Germany
H	Climate Control (1972 on)
I	Not used
J	Ford Parts and Customer Service Division
K	Import Release
L	Ford Customer Service Division Power Products
M	Performance and Special Vehicle Operations
N	Volvo
O	Outside
P	Transmission and Axle
Q	Diesel Engine
R	Manul Transmission
S	Light and Heavy Truck Special Order Parts
T	Electrical
U	Fuel and Handling Division
V	Domestic Special Order
W	Axle and Driveshaft
X	Plastic and Trim
Y	Special Vehicle
Z	Ford Service Parts, Product Analysis
1	European Product Development Center
2	Land Rover
3	Large and Luxury Vehicle Center
4	Truck Vehicle Center
5	South America Operations
6	Otomobil Sanayi, Turkey JV
7	Transmission and Axle
8	Hybrid and Electric Vehicle
9	Asia Pacific and Australia

       The fourth character represents the Engineering Operations area responsible