This geared diff for the Cougar SVR is an option that offers different driving characteristics and gives the benefit of low maintenance. The handling of the diff can be tuned by changing the oil.
A recommended starting point is 5,000 cSt (CR219). Recommended options oils would be 3,000 cSt (CR217) and 7,000 cSt (CR221) Changing to a thinner oil will give the car more straight line drive, thicker oil will give the car more stability.
It does not fit the Cougar SV2.