After the rearend was fully installed, we added gear oil. Once the driveshaft is bolted up, Turbo Direct recommends driving for about 30 minutes on surface streets to let the gears warm up before hopping on the highway or hitting the dirt. We've put more than 1,000 miles on in less than three weeks and haven't discovered any problems. In fact, it drives no differently from the OE rearend. Another plus of the Project 875 is that virtually no ground clearance is lost as compared to the Toyota axle, and it actually affords more clearance than a Ford 9-inch or Dana 60.