The 1999-2004 Mustang Cobra IRS Differential Cover is cast in aluminum, a material prized for its unique property of strength without the weight of steel or cast iron. Yet aluminum is not as flexible as steel, so when you push your Cobra to the limit in the corners or at the drag strip, you may be applying enough force to twist the cover beyond it's ability to flex. Repeatedly doing this causes the cover to fatigue & ultimately crack. You see the signs of this flex early on with the evidence of gear oil leaking from the diff cover seal.
Without resorting to a replacement cover made entirely of steel or iron, BilletFlow designed the steel brace offered here. Installation is straightforward using the supplied grade 8 hardware, and BilletFlow even thoughtfully included a hole to permit easy access to the differential fill plug without the need to remove the brace.