The gear is part of JVC 185505303ZT Reel Motor assembly. It is attached to reel motor shaft. The gear can tend to crack during the time and tape drive can become more noisy or does not work correctly.
Replacement part was created using a semi-professional 3D printer using durable Nylon material. You can find the gear here in schematics:
Gear is compatible with following JVC devices:
However, it might work also with other devices – just check your service manual.
The gear is available in e-shop