Suggest to add lubricating oil, it can be reduce the friction between the metal gears, also the sound will be smaller when it is running.

The main gear and pinion gear combo Compatible with WLtoys 104001 1/10 RC Car Only.
Made of high quality metal material,strong and durable in use.
Easy to install and upgrade your rc car.
effectively improve the performance of your car.
A grear replacement part for your rc car.

Item Name: Differential Main Gear & Pinion Gear
Material: Metal
Main Gear:70T;Pinion Gear:22T
Main Gear hole inner diameter:6mm;
Pinion Gear Hole Inner Diameter:3.17mm

Motor Gear Height: Approx. 12mm
Main Gear Height :Approx. 35.5mm

70T Main Gear Diameter: Approx. 43mm
22T Diameter: Approx. 19.5mm

Package List:
1 x 70T Spur Gear
1 x 22T Motor Gear