The outdrive IS the upper and lower gearcase. Do you mean by not removing drive? The answer is no. If you mean seperating the two halves, then yes, you can just remove the input drive gear. As the ball gears are Loctited to the shafts, you will need a press to remove them. And seals are some of the least expensive parts in a drive; no excuse NOT to change them. 'nutcaseIs it ok to replace ball gears without new seals (if seals are not currently leaking)? Can I replace ball gears without separating outdrive from upper housing?