41DD765G900 MTD Trimmer

Remove the smaller set screw that keeps the gearbox aligned on the shaft. Remove the two screws on the gearbox that are closest to the engine. You may have to loosen the other 4 screws,but they are not necessary to remove, as the new gearbox comes with those 4 screws in place. You can then slide the gearbox off the shaft. Clean all dirt a ... Read more nd debris off the end of the shaft. Install the new gearbox the same way you removed the old one. Install the set screw to realign the gearbox on the shaft. Then install the two screws closest to the engine. Tighten all 7 screws on the gearbox and shaft accordingly. Start your engine and give her a go. Gearbox assembly comes pre-installed with trimmer line already so you're good to go.