Replacing the lower gearbox of a brush cutter (trimmer)

There are no tools that last forever; even the best ones fail. This is due only to mechanical damage during operation, but also to metal fatigue. Even under normal operating conditions, microcracks appear in it, which then increase to critical sizes. Replacement is also required when the bearings wear out. The most loaded element of the tool is the lower gearbox.

Tools

You will need a set of sockets and a small flathead screwdriver. The size of the keys depends on the trimmer manufacturer, and the screwdriver must fit into the technological hole located in the lower part of the gearbox housing.

Replacement process

First, you should disconnect the spool of fishing line from the gearbox. It screws onto the threaded part of the mechanism gear. It is tightened by hand, and subsequently clamped under the influence of the moment of inertia during operation of the scythe. This means that there is no need to use any tools to unscrew it.

Insert a flat-head screwdriver into the special technological hole and slowly turn the reel until its end fits into the recess of the slots.

With one hand, firmly hold the screwdriver in the selected position, and with the other, unscrew the part in the opposite direction of rotation. There are gearboxes that have a special through hole for disassembly; they are easier to change.

The gearbox is attached to the rod with two bolts. One fixes it in the center, and the second clamps it and does not allow movement during operation.

Unscrew the centering bolt and remove it from the rod.

Loosen the clamp bolt two to three turns. Remove the lower gearbox; it will come off much easier if you constantly turn the body in different directions.


Using the same algorithm, insert the new one into place, aligning the holes in the body and the rod. Insert the appropriate bolt, then screw both hardware onto the gear housing until it stops.





Place the flange to drive the coil onto the shaft splines and tighten it. The flange not only rotates the cutting element, but also protects the gearbox from dirt.

Conclusion

Before starting work, it is recommended to clean the parts from dirt and remove adhering grass from the bolt heads. The time spent on cleaning is much less than further elimination of the problems that have arisen.
When purchasing a new part, keep in mind that each company produces its own gearboxes; they are fundamentally no different, but the dimensions may not be the same. This is done on purpose, the goal is to force consumers to buy their products.

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