Originally Posted by m4a1mustang

Because it hasn't really hindered performance, and contrary to what most believe live axles are not always inferior to a independent setup.

Here's a bit of what Billy Johnson had to say on the matter over on S2KI. Billy races the Roush Mustang in the Continental Tire series and has also done some NASCAR road racing.



Ultimately you end up having to move to a IRS setup on a street car (next gen Mustang is going to be IRS), but not necessarily for performance reasons. For one, you don't have to design a chassis with a big ole hump in the back to fit the rear axle. This gives you more efficient use of space and would actually make the rear seats of the Mustang useful.

There are more reasons we could get into, but the bottom line is as far as performance goes, the solid axle is not the crutch that most like to say it is.