Ford Differentials. Joseph Palazzolo
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engine and were found on many higher horsepower cars and trucks.
Of the four versions of the N case, three have an actual “N” cast into it right above the pinion cartridge.
The fourth version did not have the “N” in the casting on the outside but still retained the rib structure. In order to verify a nodular unit, you need to look on the inside of the casting. These have a C4AW-4025-B casting part number next to the adjuster nut.
Of course, if your budget allows, you can purchase an aftermarket iron case that is stronger than any factory case. If you are looking for an N case or think that you have found one of these desirable axles, make certain to examine it closely. The WAR, WAA, and WAB cases have the same ribbing as the N case, but are missing the ever important “N” feature.
Any of the W-series cases do have a fill plug machined in them. Both standard and W-series cases are made out of gray cast iron. Only the N-series cases are made out of the stronger, more desirable, nodular iron. While the iron is molten, magnesium is added to increase the shear strength of the alloy. The magnesium addition causes the grain structure to change from flakes to nodules and thus the name “nodular” iron. The N cases typically came with the larger Daytona-style pinion support bearing, and 31-spline axle shafts.
This chart references the connection between the month codes and the actual month. The letters I and O are skipped to avoid confusion with the numbers one and zero.
Pinion Cartridge
There are even different pinion cartridges that have been available from the various production years and models for this axle. The Daytona-style cartridge allows for a larger pinion head bearing when compared to the standard pinion cartridge. This is a great upgrade component to use for high-power applications or if you are replacing your cartridge.
Housing
Like most Ford axles, the 9-inch has a single hypoid ring gear mounting distance, so, unlike the Dana and GM axles that require unique differential carriers based on ratio, a single differential carrier works with all of the Ford ratios. Also, since this axle is used in so many circle-track race cars, the 9-inch enjoys an unparalleled availability of different gear ratios in the aftermarket.
This case looked like a nodular unit from the front regarding rib structure but did not have the “N” on it. When you look on the inside, you see WAB-4025A. This is not a nodular unit.
The desirable N-style, nodular-iron gear cases are available in four different versions. There are three versions with external Ns cast in; note the more curved style on the top right. The unit on the top left seems to be nodular iron but requires a little more investigation to verify.
This is when making a few phone calls to reputable axle builders can be helpful. There are quite a few companies making Ford 9-inch housings to fit just about any muscle car out there, including non-Ford vehicles. (See Chapter 8 for how to install a 9-inch in a classic 1957 Chevy Bel Air as a performance upgrade.)
The aftermarket Daytona-style pinion cartridge accommodates the larger and stronger pinion head bearing. This particular pinion cartridge is well reinforced and much stronger than the stock production cartridge.
Here are the internal sides of the same three units. Now you can see the C4AW-4025-B part number on the lower left unit, which verifies it as a nodular unit.
The axle housings themselves had many different variations over time as well. These variations include different-size drum brakes, disc brakes, and wheel hub arrangements.
Since these housings were a series of stamped-steel pieces all welded together, there were many different overall lengths, tubes sections, mounting brackets, and even general constructions over the years (see Chapter 5).
The Ford 8.8-inch is very similar to the General Motors (GM) 8⅞-inch, 12-bolt axle. Some differential experts tell you that the Blue Oval engineers copied the 12-bolt design when they came up with the 8.8-inch axle. While the 8.8 is similar to the 12-bolt, it isn’t identical. Interestingly, the Ford axle uses the exact same size of tapered roller bearings as the GM 12-bolt. The Ford version uses larger axle shafts and different lube flow strategy. These axles did have metal axle tags similar to the 9-inch axles but they were slowly phased out as vehicle programs were updated. There are several reasons for this.
Cost and complexity are two. These tags provided information for the service technicians but wasn’t that important for the vehicle assembly plants. The third reason was basic health and safety concerns for the assembly technicians and other employees who handled the axles in the manufacturing and assembly plants. There were many instances of cuts and scratches from the thin steel cuts and scratches from the thin steel tags sticking up on the axles.
The tags were replaced with adhesive labels that are placed around the axle tube near the brake and wheel end. These labels have a specific code that is similar to the axle code on the 9-inch axles.
This is an example of the brakes that fit the small wheel end bearing for a 10 x 2-inch-wide drum brake on the left and a 10 x 1¾-inch on the right.
Axle Flange Sizes
The chart above summarizes the three flange-style dimensions for currently available units. The large bearing flange can have any of the three sizes of clearance holes listed. The 3/8-inch holes were found on the 1978–1979 model year pick-up trucks, Broncos, and some Lincoln Versailles; the 1/2-inch clearance hole is the most common; and the 7/16-inch hole is extremely rare.
The diagram at left shows the typical wheel-end flange configuration. There are various different outside shapes. Some have a D-shape, full circles, and two flats, and while others have five holes instead of four.