Wavetrac Differential, FORD 9-INCH 31T 

Wavetrac diffs are state-of-the-art helical gear differentials designed, developed, and manufactured in the USA by Autotech Driveline. The Wavetrac Differential is the only torque biasing differential on the market with patented technology that mitigates wheelspin when an unloaded wheel condition arises. During zero axle load conditions, the Wavetrac cam device acts to create internal load, maintaining drive on the gripping wheel instead of acting like an open diff (and going nowhere!). Super strong 9310 alloy steel gears are enclosed in case-hardened steel bodies, held together with ARP fasteners. All Wavetrac differentials include a transferable, Limited Lifetime Warranty. 3 1/16" case (3 1/16" bearing OD) Fits Ford 9" with 2.891" or 3.062" case. 45 degree pressure angle.