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
This gear head fits Stihl FS56RCE FS91R FS70R FS94R FS111R FS131 FS91 and similar models that share the same shaft interface. Always verify your trimmer’s model and part number against the full compatibility list to make sure the housing mount and drive splines align.
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 fit my Stihl FS91R and reuse the original shaft and guard, or is it only for certain versions?
Yes, this replacement gear head is made for the Stihl models listed, including the FS91R, and matches part number 4180 640 0114. As long as your machine is one of the specified models and uses that gearbox part number, it should mount to the existing drive tube and work with the original guard and cutting attachment setup.
Q: I have a Stihl FS56RCE—do I need to grease this gearbox before using it, and how often should I service it?
It’s a good idea to check the gearbox grease before first use, even on a new replacement head, and add quality gear grease if it looks low. After that, service it periodically depending on use—heavy trimming or brush cutting usually means checking grease more often to keep the gears from running hot and wearing early.
Q: What’s involved in replacing the gearbox head on a Stihl FS131R, and do I need any special tools to line it up correctly?
Installation is usually straightforward: remove the cutting head and guard as needed, loosen the clamp fasteners, slide off the old gearbox, and install the new one onto the shaft tube. Make sure the drive shaft seats fully into the gearbox before tightening everything down, and then confirm the head spins smoothly by hand before starting the unit.
