1983 Grave Digger:
Win season one in cash grab mode under the normal difficulty setting.

20th Anniversary Grave Digger:
Win season two in cash grab mode under the normal difficulty setting.

The Incredible Hulk:
Win season three in cash grab mode under the normal difficulty setting.

Championship truck:
Win a season under any difficulty setting to unlock the championship version of the truck that was used.

IP/Inland truck:
Complete season one in any mode under the hard difficulty setting with a championship truck.

Big Yellow:
Complete season two in any mode under the hard difficulty setting with a championship truck.

Hooch:
Complete season three in any mode under the hard difficulty setting with a championship truck.

Dog Pound:
Complete season one in any mode under the extreme difficulty setting with a championship truck.

Hint: Jumping:
Hold Up, release, then press Down.

Hint: Wheelie:
Hold Down, then press X.