GM 12 Bolt 8.875" Street Gears, 4 Series - 4.10 Ratio Product Code: 629-0031 Richmond Gear. Fits all 4 series carriers (original ratio of 3.73 and numerically higher). 8.875” ring gear diameter, 1.625” diameter pinion, 30 spline, 8620 alloy. Primarily for street, oval track, and lightweight drag racing applications. Got these from Mark Williams Enterprises. List at $208 currently. Have maybe 1000 miles on these (barely broken in). Replaced with 3.55 and Tremec 5spd. $100 + shipping USA