Differential Gear is very important part in any real, or RC vehicles. It enables vehicles to properly drive out in corners in normal on-road driving.
Why need diff-lock?
For better traction and grip in off-road conditions, diff gears can be locked, enabling the motor's power be distributed to each wheel evenly, and minimize wheel being stuck in obstacles.
This diff-lock gear can be easily installed to tamiya grasshopper (or hornet, or other vehicles such as lunchbox, which uses the same live axle gearbox).
3 diff-lock gear is need per each gearbox. (Use copy function in your slicer software)
Printed output maybe a little stiff to fit in the center gear, a little trimming may required.
Check out my youtube channel on how to install diff-lock into grasshopper's gearbox
https://youtu.be/vF2HlVyM9Rk