The gravmod.zip file you have requested: Modifications / Other / GravMOD v1.0 - 49.01kb is not available. Perhaps try browsing all files for the game Grand Theft Auto: Vice City and upload any files you want to share or are missing. This is the only information we could locate:
You can jump from rooftop to rooftop, fly by using the number keys, and when negative gravity is enabled...make cars fly up into the air just by shooting them! The program allows you to either increase or decrease the gravitational pull in the game.