This is the 3rd gear synchronizer (synchro) ring used in your 300ZX's RS5R30A manual transmission. This soft brass synchro is responsible for helping maintain smooth and seamless gear changes. When these synchros wear the most common symptom is a 'grind' when shifting.
Synchro wear is greatly increased when using GL-5 gear oils, which are highly corrosive to the soft yellow metals used inside of Z32 transmissions. For that reason we ONLY recommend using Red Line or Motul fluid in your transmission.
- 1990-1996 Nissan 300ZX (Z32)