Performance Differential Ring and Pinion (10 Bolt) good year # 35 1975 – 1986 Pontiac Bonneville CSH29SM 1975 – 1986 Pontiac Bonneville 1975 – 1981 Pontiac Catalina 1977 – 2002 Pontiac Firebird 1978 – 1980 Pontiac Grand Am 1977 – 1983 Pontiac Grand LeMans 1977 – 1987 Pontiac Grand Prix 1977 – 1978 Pontiac Grand Safari 1977 – 1981 Pontiac Laurentian 1977 – 1981 Pontiac LeMans 1977 – 1986 Pontiac Parisienne 1977 – 1979 Pontiac Phoenix 1976 – 1977 Pontiac Ventura Author: MoPar 438 (Inch) Pinion Spline Count 27 Ring Gear Bolt Quantity 10 Ring Gear Material 8620 Steel Ring Gear Outside Diameter 7 – 1990 Cadillac Brougham 1982 – 1984 Cadillac DeVille 1982 – 1990 Cadillac Fleetwood 1985 – 2005 Chevrolet Astro 1995