* 4L60E: A four-speed automatic overdrive transmission. This was very common.
* 4L80E: A four-speed automatic overdrive transmission, usually found in heavier-duty trucks or those with larger engines.
* NV3500: A five-speed manual transmission.
* SM465: A four-speed manual transmission (less common in '97).
To know for sure what transmission is in *your* 1997 Chevy truck, you need to check:
* The vehicle's identification number (VIN): A VIN decoder can tell you the transmission code.
* The sticker on the driver's side doorjamb: This often lists the options and may include transmission information.
* The transmission itself: Look for a tag on the transmission case.
Without more specific information about your truck, it's impossible to say definitively which transmission it has.