10044013, YDGF9-28-SM ** Fits Ford 9" All Ratios -28 spline -4-spring, clutch style positraction -Internal gears are manufactured using forged 4320 steel and cut to provide stronger teeth -Fully rebuildable -Assembled in the USA Technical Notes: This unit has 1.783" bearing journals. This unit will not fit in Strange Engineering aluminum dropouts. DTA recommends the use of high grade GL-5 gear oil and Limited Slip Differential additive for long life and smooth operation. Part number OILADD or 43161. The use of synthetic oil is allowed but may result in aggressive or noisy operation. This unit requires the use of ring gear bolt part number D8OZ4216A.