More than likely they are talking about this bushing:
Solid:
https://www.z1motorsports.com/suspen...37-p-7517.html
Urethane:
https://www.z1motorsports.com/suspen...37-p-5801.html
Its a common issue with the 350/370z's. The dealer will just replace the entire subframe because the diff bushing isn't serviceable from the factory.