GM 8.5 10-Bolt Ring and Pinion Set, 3.73 Ratio 30-Spline

Motive Gear GM10-373A ring and pinion set, 3.73:1, for the GM 8.5 inch and 8.625 inch 10-bolt axle with a 30-spline pinion. The gears are cut from 8620 steel and heat treated. This set is the 2.73-and-up cut, so it bolts to a standard carrier case - if your axle runs a 2.73-and-numerically-lower carrier you need the other case, not a different gear set. Cross references GM 26037712 and 26066706, Richmond Gear 49-0041-1, Dorman 697-301, Motive Gear GM10-373 and Richmond EXCEL GM85373.

The GM 8.5 10-bolt went into rear-drive Chevrolet, GMC, Cadillac, Buick, Pontiac and Oldsmobile vehicles from 1970 through 2020 - Silverado, Tahoe, Suburban, Yukon, Escalade, Camaro, Impala and the G-body cars among them, plus front axle use on some 4x4 applications. Count the cover bolts and measure the ring gear diameter before you order. The 8.5 and the 8.625 share this gear set; the 8.2 and the 7.5 do not.

Most people put 3.73s in for one of two reasons. Either the truck went up in tire size and lost its launch and its converter is now flashing wrong, or the original gears are howling and pitted from a low fluid level or a failed pinion bearing. If you are regearing for tires, 3.73 is the common step for a stock-ish half-ton on 31 to 33 inch tires. If you are replacing broken gears, inspect the carrier bearing journals and the axle housing before you reuse anything - a gear set that ate itself usually took a bearing with it.

This is the gear set only. You also need a master install kit with carrier bearings, pinion bearings, crush sleeve, pinion seal, shims and marking compound, and both axles have to come out to do the job. Set pinion depth first with the shim pack behind the inner pinion bearing, then set pinion bearing preload by crushing the sleeve, then set carrier backlash with the side shims to the figure in the GM service manual for this axle. Paint the teeth and read the contact pattern on both drive and coast sides before you button it up - depth and backlash both move the pattern, and getting one right while the other is wrong is how a fresh gear set gets noisy in a thousand miles. Torque the ring gear bolts in a cross pattern and run the vehicle easy for the first heat cycles to break the gears in.