So I've had my 91 300zx TT (auto) for about a week now and I notice when I'm cruising anywhere from 40+ mph the transmission down shifts and the rpms shoot up but the car doesn't really accelerate. Once I let off the gas it is fine. I thought it was only an issue when overdrive was off but it did it the other day while in overdrive. The engine will continue to rev unless I let off the gas. Does anyone know what could be the cause of this? Could it be that I just need new transmission fluid or is there something actually wrong with the transmission itself? Any input would be appreciated, thanks.

 

Sounds like a software bug if that's possible.