NASCAR Rumble Codes -

All tracks, legends, and cars:
Select "Game Options" at the main menu, highlight "Load and Save", press Left, then press X to enter the password screen. Enter C9P5AU8NAA as a password to unlock every track, legend and car through the pro level.

Elite class, hidden FMV sequence:
Select "Game Options" at the main menu, highlight "Load and Save", press Left, then press X to enter the password screen. Enter KMZWA8AWAA as a password to unlock everything including all cars (with Elite class, which is higher than Pro) and the hidden FMV sequence.

Hint: Wrenches to access hidden cars:

Chicken truck
Located in a chicken hut on the "Fowl Play" track.

Sprint car
Located in the last shortcut on the 'Dog Tired' level. Turn left at the track.

Jet car
Located on Bad Lands - Stoney Creek. On the last turn of the track hit the jump going left. You should land on a shortcut. Turn around and return towards the end of the short cut. The wrench will appear in front of you.

EA Sports car
Successfully complete the EA Tournament in rookie mode to unlock the EA Sports car in rookie mode. Successfully complete the game in pro or elite mode to unlock the EA Sports car in those modes.

Golf cart
Located in Big Easy - Mardi Gras. In the middle of the track, take a shortcut right through a house. Go to the last room and turn right at the bookshelf. Break the wall to find the wrench.

Hotrod
On Metropolis - Night Flight, go up the blocked off ramp just before you get to the building where you normally jump across to break the glass. Stop and fall down, go to the left, and you will unlock the Hotrod.

Tow Truck
Play the Metropolis - Ship Shape track in single race mode. Go behind the starting line until you see a road off to the right (going backwards). There will be a wrench there that unlocks the Tow Truck.

Road Captain
On Southern Exposure - Hog Hollow, go to the gas station towards the end with the barn next to it. Ram the barn doors to find the wrench that unlocks the Road Captain.

Loader
On Gold Rush - Golden Rule, after starting your race go either the top or bottom route when the track splits. Turn around after coming out of the caves and you will see two caves on the lower track. Go into the cave on the right and you will unlock the Loader car .