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Aftermarket Axles for Your Mustang

Author: Glenn Cope II

The live axle rear ends on S-197 Mustangs from the factory are said to be good. They have been upgraded from the older 28 spline of previous years. The older 28 slpine rear axles would hold up to around 400 rear wheel horse power before they started to get into a breaking point. The 05-10 Mustang 7.5" Rear End used a 28 spline Rear Axle, while the 05-10 Mustang 8.8" Rear End used a 31 spline Rear Axle. StarPng in 2011, both the V6 and 5.0L GT Mustangs were built with a 31 spline 8.8" Rear from the factory. This was good enough for street cars but once you modified your engine or put on some drag Pres it was Pme to consider an axle upgrade.

The more splines the larger the axle is, increasing its strength considerably. A 31 spline axle for the 8.8 is about 30% stranger than the 28 spline axles. Now even though the newer 31 spline axles are stronger they are sPll mass produced with minimal quality control so they can roll off the assembly line at a reduced cost. Many Ford OE axles are made of SAE 1055 or SAE 1541 carbon steel and are inducPon hardened. This means only a porPon of the depth is hardened while the rest of the axle steel remains unhardened.

Now if you are going to be pushing more than 500 rear wheel horse power and planning to do some drag racing you will want to strongly consider a high quality aftermarket axle, units built for the drag strip. Axles that are built to be subjected to the high torque and demanding stress loads.

When looking at a[ermarket axles you will also want to check that your rear differenPal will be compaPble with your upgrade. Moser, Superior and Ford Racing are all excellent brands to choose from. You can either replace your axles with aftermarket versions that have the same amount of splines, or upgrade to an axle with more splines and a larger diameter for added performance. If you choose to use the same number of splines it is easier install them yourself. If you are choosing to upgrade in size you will need to change the rear end differenPal. That gets a bit more complex and you may need to get a new differenPal to match your axle choice.

If you are planning on doing a lot of drag racing then you should look into an aftermarket set of rear axles that have what is called a C-clip eliminator opPon. Your factory axles are held into the rear end differenPal with C-lips that fit into a groove on the end of the axle. If these factory C-clips or the grooved end of the axle break then the axle can come out of the housing tube resulPng in the whole wheel flying away from the car. NHRA rules ban C-clip axles on any mustang running 10.99 or quicker. The c-clip eliminator consists of a new axle bearing and a retainer plate that bolts to the end of the axle housing keeping the axle from coming out of the end of the housing in the event that it breaks.

So, before the next Pme you dump the clutch on the starPng line at the strip, consider upgrading those axle shafts.