Overview
This aftermarket gear head and trimmer head replaces the worn or damaged gearbox on your string trimmer or brushcutter. The kit ships with a bump-feed trimmer head, giving you a ready-to-use setup as soon as the gear head is mounted. When the original gear head develops play, leaks grease, or makes grinding noises, swapping in a fresh unit is far more practical than rebuilding the old one.
Key specifications
- Type: aftermarket replacement gear head
- Pre-greased: yes
- Material: die-cast aluminum housing with steel gears
- Includes: bump-feed trimmer head
Compatibility
Compatible with Stihl FS56RCE FS91R FS70R FS94R FS111R FS131 FS91 and other trimmers sharing identical drive-shaft geometry. Cross-reference the OEM part number listed in your owner’s manual with the compatibility table to confirm this gear head will work on your machine.
Installation notes
Detach the worn gear head by removing the clamp bolts at the shaft junction. Wipe the shaft clean and inspect for burrs. Press the new gear head onto the shaft until the splines seat, then torque the clamp bolts firmly. After mounting your trimmer head or blade, let the unit idle for a moment to confirm the gears are meshing properly before applying load.
Common questions
Q: Will this 25-2 trimmer head and 4180 640 0114 gear head fit my Stihl FS91R or FS56RCE without modification?
Yes, this replacement is made for the Stihl models listed, including the FS91R and FS56RCE, so it should match the standard straight-shaft setup used on those units. It’s still a good idea to compare your original gear head part number and shaft configuration before installation, especially if your trimmer has had previous aftermarket repairs.
Q: Does the 25-2 trimmer head come ready to install on an FS70R or FS94R, and do I need any special tools to change the gear head?
On the FS70R and FS94R, installation is usually straightforward if you already have access to the shaft housing and locking pin for the head. You’ll typically need basic hand tools, and it helps to clean the shaft end and grease the new gear head before use so the drive connection seats properly and runs smoothly.
Q: How often should I grease the 4180 640 0114 gear head on my FS131R or FS111R after installing it?
For heavier-use models like the FS131R and FS111R, checking the gear head grease periodically is important, especially if you use metal blades or run the machine for long sessions. A small amount of the correct gear lubricant at regular service intervals helps reduce heat and wear, and you should also stop and inspect it if you hear grinding or notice the head getting unusually hot.
