I’ve had my 07 G35 Sedan (Automatic) for a few months and ever since I bought it, it’s had an issue to where when you floor it from 0 MPH, it only does 3,000 RPM and when speed increases the RPM steadily rises and the car doesn’t shift, yet it still reaches 100+ MPH, to me it sounds like it is stuck in a higher gear. Does anyone know what this could be?

 

I'd take it to Nissan/Infiniti for a diagnostic.