從我張陳年GTB說明書話:
3.5R: 4 teeth lower pinion than normally used on 6-7 turn brush motor
4.5R: 3 teeth lower pinion than normally used on 8 turn brush motor
5.5R: 2 teeth lower pinion than normally used on 9-10 turn brush motor
6.5R: 1 tooth lower pinion than normally used on 10-11 turn brush motor
7.5R: same pinion as normally used on 12-13 turn brush motor
8.5R: 1 tooth higher pinion than normally used on 13-17 turn brush motor
10.5R: 1 tooth higher pinion than normally used on 19 turn brush motor
13.5R: 2-3 teeth higher pinion than normally used on 27 turn brush motor