Detroit Truetrac Differential GM 10-Bolt1971-89 GM Car1972-89 GM Truck 28-Spline Axles 8.5'' Diameter Ring Gear Fits 2.73 & Up Gear RatiosRear Only All GM 8.5"/8.6"Eaton differentials require special bearings. For 28 spline axles with small bearing bores (race O.D. of 2.89"), usually found on vehicles prior to 1999, bearing LM-102949 and race LM-102911 are required. For 30 spline axles with large bearing bores (race O.D. of 3.06"), usually found on vehicles from 1999 to present, bearing LM-603049 and race LM-603012 are required.Note: 1998 - Earlier use 873-D1585 Spool Bearings, 1999 - Later use 873-D1582 Spool Bearings.