what size pinion
 

just bought a used xray t3 comes with 84 teeth 48 dp spur gear what size pinions do you guys recommed in my current tc5r i use 64 dp of 100 spur 41 pinion giving about 5 fdr but not sure about 48dp thanks for any replies

You'll have to do a bit of maths, depending on the internal ratio of the XRAY.

JIggling the equation around you get...

pinion = (spur * internal ratio) / final drive ratio

the internal ratio of the xray t3 is 1.9 so going on your sums should be around a 32 pinion for a fdr of 5 thanks for the info