The 2001 Chevy S10 with a 4.3L V6, even if it's a New Venture 3500 transmission, typically uses
GL-4 or GL-5 gear oil. However,
checking your owner's manual is crucial. The exact specification (weight and type) will be listed there. Don't rely solely on generic information.
Using the wrong type of fluid can severely damage your transmission. The owner's manual will provide the manufacturer's recommended fluid for your specific vehicle.