The way the splines are created makes a difference too. For example, a 700-hp full-race drag car with slicks and a transmission brake would put more stress on the driveline than a street-tired foot-brake car with 1,000 hp. When it comes to spline count, there isn’t a magic formula or number for determining axle strength because other variables are at play, such as tires, transmission, intended use, etc. Manufacturers offer guidance for a particular vehicle, engine, transmission, and other factors, so you can select the correct axle shafts for your combination. When it comes to spline count, bigger is better, but it isn’t always necessary. So arbitrarily upgrading to a larger count costs you money that may be better spent elsewhere. Therefore, the 30-spline axle is 35 percent stronger than the 28-spline.Īnytime you increase the spline count, the differential carrier must be upgraded to match the axle diameter of the particular shafts. The actual outside diameter (OD) of a 28-spline axle is 1.205 inches while the 30-spline axle is larger at 1.310 inches. Most 8.5-inch 10-bolts installed in trucks received 30-spline axles. Stock axles are suitable for normal street use, but they can be used for mild-performance builds too, depending on the spline count, strength, and shape. In the final analysis, the axles used in your housing are just as important as the gears and differential. And if you add more power and harder driving conditions, they simply must be capable of taking a beating. Most high-performance cars run sticky tires, so these forces dramatically increase, putting several hundred tons of force on the bearings and the 1/4-inch-thick area that retains the C-clip.Īxles are tough components that, even in stock vehicles, take a lot of abuse. Every corner means that the one axle is pushing in on the wheel bearings and crossshaft pin in the differential, while the opposing axle is pulling on the C-clip. Therefore, the bearings need to be in good condition and the axle surface they ride on needs to be perfectly round and smooth.Ī typical street axle must cope with enormous side loads. The axle bearings, or wheel bearings, must support the entire weight of the vehicle. Both GM 10- and 12-bolt differentials are a semi-float design, which means that the axles carry the weight of the vehicle on one bearing at the end of the axle shaft. Other loads are at work on the axles as well. Note that the shape of the splines are the same. The difference is nearly 1/4-inch diameter, which is an increase of approximately 33 percent. Here, a 28-spline axle (left) is com-pared to a 33-spline axle (right). Too much torque load for the axles results in a rotational fracture and axle failure. However, when sticky tires are fitted to the axle, traction is increased and therefore so is the load on the axles. If the tires spin from heavy acceleration, this number decreases.
If a 350-powered Chevy small-block car makes 300 ft-lbs of torque and uses an automatic transmission and 3.55:1 gears, each axle receives more than 2,300 ft-lbs of torque. Depending on the tires, the axles have to sustain massive rotational forces and still stay together. Dump the clutch for a manual, and the shock is even bigger. Thousands of foot-pounds hit the axles every time you stomp on the gas pedal. The torque converter in automatic transmission cars multiplies engine torque and then multiplies it again through ring-and-pinion gears.
The axles see the most brutal application of torque for the entire vehicle. Axles are simple components that have a long shaft with splines on one end and a flange on the other, which is drilled for the wheels.
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