I have a General tranny question.3gear trans, I plan on racing both 17.5t class and mod class, probably a 7.5t for example purposes. If i leave the 69 spur for the 17.5 setting per manual gear chart, can i just use a lower pinion for the 7.5 and if so, is there a difference is how the car will feel with the smaller pinion & spur for the mod?? formula i used was tranny 2.60x69(spur) divided by pinion(18) i came up with 9.96 any insight would be greatly appreciated..