Gearing

[mxracer]

I have a nitro rustler with a TRX 2.5 in it.
When I had my lucky day I had to put masher 2000's on.
The stock sper gear is 70 tooth,I put in a 72 tooth is any other gearing necessary. :\

 

[bourney2006]

just make sure the spur and pinion mesh right (not too tight or slack) other than that your fine.
By changing spur gears, pinions etc you change the gear ratio. To find out your ratio simply divide the spur by the pinion.
hope that helps

 

[mxracer]

So a 20 tooth cb and a 72 tooth sper is
72/20=3.66635736743574375358 lol
3.6

 

[bourney2006]

i think your is a 3.6:1 ratio
That means your pinion gear has to turn 3.6 times to turn the spur gear 1