In today’s high-performance world the line between street and race is a blurred one, particularly under the hood. As the street-driven Drag Week cars flirt with the five-second zone and speeds close to 250 mph, there is no doubt that Pro Mod engines on the street is considered normal in some households. Moving into the real world, at times it seems like even the most mundane looking street cars in most neighborhoods are belting out 1,000 hp. But as the question of street or strip becomes blurry under the hood, there is a very clear difference in the axles one chooses for their ride. Strange Engineering designed two separate custom axle lines—Pro Race and Alloy—for specific reasons.
For the street crowd, the Strange Engineering Alloy axles are the go-to product when selecting a pair of custom axles, which includes fitments from 28-spline up to 35-spline sizes and is available for the popular rear-end housings like Ford 31 spline 8.8 inch and 9 inch, GM 10 bolt and 12 bolt rear-ends, and Chrysler Dana 60. The Alloy axles are made from a high-forged alloy steel, are CNC-machined, and there is just a two-day turn around time on custom axles ordering. The Alloy axles are induction hardened, which means the metal is heated by an electromagnet and then rapidly cooled (quenching). The deeper depth of the case hardening of the axle increases the torsional strength, in conjunction with the proprietary Alloy material. Through this process the axle can withstand tremendous power while still being able to handle lateral and bending loads.
The term flexible isn’t normally associated with axles but in the case of the Alloy axles it is an advantage. On the street there has to be a give and take relationship in regards to the rear axles. They have to be sturdy enough to endure the brunt of sticky tires and big power but also be flexible to withstand the tension in everyday driving. As a vehicle makes turns on the street (for example), the splines are subjected to stresses that are not normally associated with straight-line performance. The flexibility in the Alloy axles allows the component to survive the street abuse but the axle’s shape and hardening process keep it strong enough for drag racing abuse.
On the other end of the spectrum are the Strange Pro Race axles, which are found in many levels of drag racing, including the professional ranks with 8,000 hp. Strange Engineering doesn’t recommend the Pro Race axles for street use because they are constructed from Hy-Tuff alloy steel, which has been used in military aircraft. The Pro Race axles are through hardened, which means the components are heated to temperatures above the transformation range and cooled quickly. The result is an axle with an extremely high tensile strength (240,000 psi) but retains its ductility. The stresses of street use, particularly the bending loads seen in everyday driving like speed bumps, railroad tracks, and potholes can cause stress fractures in the flange or bearing journal, which could lead to axle failure. It is the flexibility of the Alloy axles that allow those axles to live on the street.
It should be noted that with all the heat treatment, Strange Engineering does all of its machine work on the splines prior to heat treatment. That allows for consistent heat treat depth, leading to a stronger axle. Some companies heat-treat the materials before the splines are machined into the axle, which causes it to be weaker despite the shiny look.
Of course when the money is on the line in a dedicated drag racing effort and every ounce of horsepower and torque must be transmitted to the tires, the Pro Race axles are the product to get the job done. The axles are more than just strong units; Strange Engineering offers several options for its Pro Race axles that include two different lightened flange options and 40-spline axles can be gun-drilled for even further weight savings. The company also pays contingency prize money at most associations for the use of their Pro Race axles.
There might be a lot of dual-purpose components on a street/strip vehicle but axles aren’t on that list. Choose your components wisely to ensure the ultimate performance at the track or trouble-free street miles from your muscle car or hot rod.