If you're looking to replace the rear gears in your Mustang or repair a broken housing, the Ford Performance loaded differential housing will get you up and running in no time. The loaded housing features M-4209-88355A Mustang IRS super 8.8" ring/pinion set and M-4204-M traction-lok differential. The gears are pre-installed, set, and ready to roll with no additional difficult gear install needed. Installing this loaded housing is an easy way to make your 3.15 or 3.31 geared Mustang accelerate quicker.