Buy a new circlip (just in case) flick the old circlip off, pull the shift lever off. CLEAN the stud and bolt hole. Reinstall the stud, ideally with lock-tite on it. Can't remember the torque.
Grease that shaft, put the lever back in, install circlip. Slather the top of the circlip with silicone to stop it coming off. (Less likely with a new circlip but do it anyway)
Grease that shaft, put the lever back in, install circlip. Slather the top of the circlip with silicone to stop it coming off. (Less likely with a new circlip but do it anyway)
