to the braking loads. The brake drums and wheel cylinders (or calipers and rotors) are mounted to the wheel ends of the tubes. Some axle housings even locate the vent fitting in the top of one of the axle tubes.
Here is the renowned Ford 9-inch beam axle housing. This axle stand has some interesting features. On the right tube-support upright, there is a screw thread arrangement to allow us to raise this side during the straightening process. This custom-built axle housing straightening stand has a right-side support that can be raised while heat is applied to the correct spot of the housing. Also, the housing is strapped down to concentrate the tweaking force properly.
Banjo and Salisbury Axles
There are two main types of beam axle housings—banjo and Salisbury—and both of these styles are still in production today. Toyota and Mitsubishi are a couple of the vehicle manufacturers that use banjo axles today while most other manufacturers have switched to Salisbury. All Salisbury beam axles have a cast center section.
There is an interesting history behind the term Salisbury axle. In 1901, the Salisbury Wheel Company was founded in Jamestown, New York. The founder, C.W. Salisbury, patented an automobile wheel. He was a key maker and repaired umbrellas by trade. He paired up with Scott Penfield and E.D. Sherman to start his manufacturing process. Their first customer was the producer of the Thomas Flyer Automobile, E.R. Thomas Company.
The Ford 9-inch banjo-style axle has a cast center section that is painted black and is removed from the front of the axle housing. A series of weld seams joins the multiple pieces, which eventually make up the entire beam portion of the housing.
An assortment of the Ford 9-inch center sections is waiting for a new home in a vehicle. Most reputable shops have a decent inventory of such parts.
The cast center on a typical banjo-style axle housing is shown in light blue. It supports the hypoid gears and the differential. The housing tube portion (yellow) consists of a series of stamped and welded parts with the remaining shafts and hardware being similar to other axles. (Dana Holding Corporation)
In 1905, the Salisbury Wheel Company started producing front axles and, in 1907, began producing rear axles. Around the same time frame, Clarence Spicer started the Spicer Company in Plainfield, New Jersey, not too far from Salisbury, and specialized in universal joints. Charles Dana, an attorney and businessman, invested in Spicer around 1914. In 1919, Spicer Manufacturing Company acquired the Salisbury Axle Company. Spicer Manufacturing is now called Dana Holdings Corporation, but the Salisbury name is still around.
This style of axle became very popular and, with the advent of World War II, many Jeeps were outfitted with this style axle. This axle style was well known in England from the Jeeps during World War II, and the English still refer to this axle as a Salisbury. Just keep in mind that these axles have nothing to do with Salisbury, England. Even today, we still associate the term Salisbury axle with an axle that has a cast center section, rear cover, and pressed-in tubes.
The removable center section from the banjo-style axle looks like this. Notice the adjuster nuts are on either side of the differential, which allow for easier adjustment of the ring gear backlash and bearing preload. The bolts hold the little tabs on the bearing caps in place and prevent the adjuster nuts from loosening up. Also, notice that the pinion bearing feed port has been cut away for easier viewing. (GKN Driveline)
This Ford stock-style banjo center section has been damaged from way too much torque. A stronger center section may have prevented this failure, but this goes to show you that the stock Ford 9-inch is not bullet proof and actually every axle has a torque or impact value where it will fail. Notice that one bearing cap is missing a section in the middle while the other is in two pieces. This failure also cracked the pinion straddle-mount bearing support and even the front of the housing cracked. There is nothing salvageable from this center section.
On this rack of axle housings, the Salisbury-style are the second one from the top and the bottom one. The other six housings (some are stacked behind one another) are all banjo-style. (Randall Shafer)
The banjo-style axle has a removable center section. This cast center section is removed from the front of the axle and supports all of the gears and bearings. Many small steel pieces are welded together to form the banjo-style axle housing. Toyota still uses this style axle housing on its truck platforms today. The most well known banjo axle is the Ford 9-inch, which will be covered later. The banjo axle, with its studs sticking out, resembles its namesake musical instrument, with the drum and tuning keys sticking out.
Probably, the most significant weakness and most common failure point of the banjo axle is at the differential bearing supports, which are cantilevered out from the cast structure. The design has two arms reaching from the main casting, like diving boards, that are trying to support the hypoid-ring-gear separating loads. Under heavy torque loads, these bearing supports can, and frequently do, break in stock form. If you are going to send tremendous amounts of torque through a banjo-style axle, it is crucial that you use a readily available aftermarket center section, or a factory nodular-iron unit that is stronger than the common, stock-gray-iron center section found on most passenger car applications.
Independent carrier axles (ICAs) utilize halfshafts instead of axle shafts to transfer torque to the wheel-end hubs. ICAs, therefore, do not react to suspension loads. The axle-carrier movement is typically independent of suspension movement. These style axles are more commonly found on luxury vehicles and ultra-high-performance cars, such as Ferraris. Certain domestic performance vehicles have also utilized ICAs. The purpose-built, limited-production 1999 Cobra R Mustangs debuted with an ICA, and all Cobra Mustangs from 1999 to 2004 were factory-built with ICAs.
The latest Dodge Vipers and Corvettes use ICA rear axles, and the reinvented 2010 Camaro has an ICA. Many folks have grafted ICAs from other applications into their muscle cars. I need to caution you on performing such a modification, as the ICA load-bearing frame members, mounts, and dampers are originally tuned for the original chassis stiffness and compliance.
When you rip that subframe out of a Jaguar or Cadillac CTS and make it fit under your Nova, chances are it will not perform the same as the original donor car because the entire rear subframe module is tuned for a specific chassis arrangement, wheelbase, and weight transfer characteristic. Keep in mind that there are companies that specialize in conversion kits for such swaps. These are expensive swaps and do not always garner the expected benefits. A custom-fabricated ICA can be a great talking point while at a car show. In some racing circles, an independent suspension may yield significant advantages, especially when there are abrupt changes in the track surface.
