18 Wheeler: American Pro Trucker Cheats for GameCube

All you have to do is complete Arcad mode with all four characters

Lizard Tail:
Successfully complete the game with all five trucks (Asphalt Cowboy, Stream Line, Long Horn, Highway Cat, and Nippon Maru) to get Lizard Tail.
Bonus parts:
Go to arcade mode and select any truck. Get to your destination ahead of your rival, then complete the bonus parking mini-game to win bonus parts.
Slip stream:
When you are behind a truck, you will get a slip stream. This will allow you to get a small boost to get in front of the truck.

Extra parking levels




Once you finish all the normal parking levels (4), you will unlock one more, finish that and you should get another.

Bonus Parking Levels:


Successfully complete each of the four parking levels to unlock a bonus parking level. Successfully complete the bonus parking level to unlock yet another parking level.




Earn a New Truck/Trucker:


If you complete arcade mode in any difficulty setting with all four original truckers then you will earn a new truck/trucker called Nippon Maru.




Earn Two New Trailers:


Complete Arcade Mode with all four original truckers in any difficulty setting to earn two new trailers to use in Score Attack Mode.




Extra Trailers in Versus and Arcade Modes:


If you complete Arcade Mode on any difficulty with all four original truckers, not only do you get the new trailers for Score Attack Mode, but you also get them in Versus Mode.




You can also use them in Arcade Mode if you select the Nippon Maru truck.