I do my burnouts in 2nd gear, never broke 1st or 2nd gear. 3rd gear is on the end of the output shaft. The 3rd gear breakage is due to the input shaft and the output shaft flexing away from the cluster gear, basically trying to climb over or away from the cluster gear from pressure [ torque ]. Less tooth engagement = stripped teeth. Possible causes , worn pilot bearing, case input shaft bearing , input needle bearing. or your engine has to much torque!