hi there i just purchased my 97 convertible z n it has the c5 corvette wheels with 245-40-17 tires n when im goin 65-70mph my rpms are at 23-2400 does this mean i have gears in my car n its auto by the way

 

Assuming your A4 trans is in O/D and the converter is locked up, assuming your tach is accurate (or did you read the RPM from the PCM with a scanner?) and using the 24.7" diameter of the 245/40-17 tires you listed, the RPM in the 65-70MPH range would correspond to 3.73 gears.

Where did you get the 245/40-17 tires? The diameter (24.7") is too small compared to the stock tires, which were either 245/50-16 (25.7") or 235/55-16 (26.1").