Originally Posted by dfiantii
Should be 3mm diff balls right.
Originally Posted by fastvee
Wobble left to right is normal(if looked from back of the car) ,but the adapter slipped out from spur and the spur started to wobble front/back. So that needs sorting,maybe gluing the adapter in the spur.
When using a standard spur gear with adapter, only use 1/8" diff balls
3mm diff balls are for the metric Tamiya type spur gear
If the Spur gear adapter does not fit snug, there will be run out, which will make proper gear mesh impossible
Try to find a Spur gear that fits the adapter better, some gears have too large an I.D. to work with the adapter, even though this should be a standard size
You can also use 64p pinion gears with the Tamiya Spur gear, in the larger sizes 30+ the mesh is close enough to work without any issues
There will always be some side to side play in the spur gear, this is normal & should never cause any problems