Before installing a new differential, decide if you want to keep your final drive ratio or change the gears. You don't want to do this job twice. This is also a good time to inspect your axles and replace your axle bearings and seals. For our Monte Carlo, we had to upgrade to 28-spline axles to match the spline count in our new Auburn carrier. Moore also rebuilt the rear, replacing the pinion bearings and seal. We did keep the car's stock 3.73:1 gears, though.