Overview
A failing gear head announces itself with excess vibration, grease leaks, and rough operation. This replacement gear head is machined to OEM dimensions and arrives pre-greased, ready to bolt onto your trimmer shaft. It is a straightforward fix that restores smooth, quiet cutting.
Key specifications
- Type: aftermarket replacement gear head
- Pre-greased: yes
- Material: die-cast aluminum housing with steel gears
Compatibility
Designed as a direct replacement for Stihl FS55 and related models. Double-check your trimmer’s shaft diameter and mounting bolt pattern in the compatibility chart, since even small differences will prevent a proper fit.
Installation notes
Remove the cutting attachment and unbolt the old gear head from the shaft tube. Inspect the drive shaft splines for damage before installing the new head. Slide the replacement onto the shaft, ensuring the splines engage fully, and secure the clamp bolts. Mount your preferred cutting attachment, start the trimmer at low RPM, and check for unusual vibration or noise.
Common questions
Q: Will this gear head gearbox fit my Stihl FS55R curved shaft trimmer, or is it only for the straight shaft FS55 models?
This replacement gear head is intended for Stihl FS55 units that use the compatible gearbox/head setup, but FS55R curved shaft versions can use a different drive configuration than straight shaft models. The safest check is to compare your original gearbox mounting tube size, shaft connection, and head attachment style before installing.
Q: Does this replacement gearbox head come ready to use, or do I need to add grease before installing it on my FS55?
It’s a good idea to check and add gearbox grease before first use, even if the unit appears preassembled. After installation, grease the head at normal service intervals and make sure the fasteners are tight so the gearbox runs cool and doesn’t wear prematurely.
Q: My Stihl FS55 gear head is making a grinding noise and the trimmer head wobbles—will replacing this gearbox head solve that?
If the noise and wobble are coming from worn internal gears or bearings in the gear head, replacing the gearbox is usually the correct fix. Before installing the new one, inspect the driveshaft, shaft tube, and trimmer head hardware too, because damage in those areas can cause similar symptoms and shorten the life of the replacement.
