The LA-4 thrust balls are used in the ZX spur gear. They are steel balls, sized 1/8 inch or 3,175mm.
It is recommended to keep this size when replacing them, as they sit snuggly into the slots of the spur. Reducing the size to eg. 3mm balls can result in a bit of lateral play with regards to the spur which can cause tiny jolts of power when accelerating or braking. The spur would also sit 0.1mm closer to the gearbox, but this shouldn’t have an impact on the pinion-to-spur alignment.
