orange drive gear andblue drin providing you havent changed the rear ratio or tire size .heres the formula DONT LOSE IT .multiply the rear end ratio times the #of teeth on the drive gear .now divide the answer by the tire size (the circumference in inches ie 28 29 30 etc )and multiply the answer by 20.2 .this number is how many teeth you need on the driven gear. easy enuff rite?www.ckperformance