If your YIKONG YK4107 RC Car has excessive gear backlash in the Differential Gear Set 18T/13T (Part no.21032), one possible solution is to add a 12 × 21 × 0.5 mm shim (for reference only) to take up the extra clearance. This can help reduce gear backlash, improve gear meshing, and lower the risk of stripped gears. Since manufacturing and assembly tolerances may vary between different YIKONG YK4107 RC Car vehicles, you may need to adjust the shim thickness accordingly for the best fit.
