The following guide will show you how to lock your ball differential. This method is fully reversible if you do not like the behaviour of the locked diff. Many RC Drifters recommend this especially for the rear diff, but it can easily be performed on the front diff as well. This gives users an inexpensive way to lock a diff so that they can make a better decision whether a spool axle is worth purchasing in the future.
For this mod I will be using a Yokomo MR4TC/Drift Package ball diff. Most ball differentials are designed the same way so this method should work for most ball diffs. This will work for both gear and pulley ball diffs.
Take apart the ball differential, then remove the differential diff balls. Store them if you want the option to be able to revert to ball diff, otherwise do what you will with them.
Find some a rubber type material to sandwich between the diff ring and the gear. This is to ensure that the gear and the diff plates do not slip, a rubber type material is better resistant to movement. I chose to use a thick rubber glove, it is thicker than traditional sterile rubber gloves. It will make up for the space the balls leave out.
Use the differential plate as an outline to cut out the rubber material to the approximate shape. Make sure to cut a large enough hole in the centre to accommodate the bearings so it does not cause any future problems.
Assemble the ball diff back together. The differential goes back together with the rubber material sandwich between the diff plate and the gear or pulley. Tighten the differential so that there is no movement. Hold down each side and turn to ensure it is locked in place.
Now re-install into your chassis and the differential should now be locked. Remember to shim the differential correctly on each side so that it has very minimal play.
Happy drifting! XD