If your Mustang has the factory transmission in it, chances are you have the factory 10 spline input shaft. All factory T56, 3650, T-45, & T-5 transmissions came equipped from the factory with a 10 spline input shaft, including 03-04 Cobras. If your T-56 has been upgraded or the factory transmission has been replaced with an aftermarket TKO, there is a good chance you have a 26 spline input shaft. This is mostly seen in high horsepower applications.
The most obvious difference of a 10 spline and 26 spline input shaft is the number of splines on the transmission’s input shaft. Similar to 28 spline vs 31 spline axles, the 26 spline input shaft allows for more contact area for a stronger, more reliable shaft under high horsepower conditions. When increasing horsepower in your T-56 equipped Mustang, swapping out the factory 10 spline for an aftermarket 26 spline is cheap insurance. The 10 spline shafts have been notorious for snapping with 500+ horsepower cars under spirited driving. Making the upgrade can prevent this and give you peace of mind to turn up the boost!
Strength is the key factor here, spreading the load over the higher spline count will support a higher horsepower application. Just like with rear axles, the higher the spline count the better for your high performance Mustang application. By doing these upgrades, you will have better reliability and also longevity out of your car.
Aftermarket transmissions options will also be a key benefit when considering the 26 spline upgrades. When considering a vehicle with a rough estimate of 500+ horsepower, the factory transmission can also be a weak link in the drivetrain. If we take the factory T5 10 spine applications, these are normally rated at 300-330 ft/lbs of torque at best. Killing two birds with one stone can come into play here, the popular TKO 600 and T56 Magnum models will be an awesome way to do this. These options will upgrade you to nearly double the overall horsepower ratings. Please note, when doing these swaps, other components will be needed, our experienced staff here at LMR can answer any question you have on these swaps.
Peace of mind is the biggest benefit when considering doing any 26 spline upgrade on your Mustang. There is nothing worse than a catastrophic failure. If any failure happens, you can wind up hurting the car more than if you addressed this issue off the bat. A lot of us daily drive our cars and need to have reliable transportation. Honestly, any way you look at these swaps, you will only be benefiting yourself.