All cars and tracks:

Enter Down, Left, Up, A, Down, Right as the password.

Level passwords:

Shadow Jet:

2 - Left, Up, Left, Down, Up, A
3 - Right, Up, Right, Down, Up, A
4 - Up, B, Up, Up, Left, A
5 - B, Left, B, Up, Up, Left
6 - Down, Left, Up, A, Up, Up
Final - Down, Left, Up, A, Down, Right

Slide Out:

2 - Down, A, Up, A, B, B
3 - Left, B, Left, Right, Down, B
4 - Down, B, B, B, Right, Down
5 - A, A, Right, Right, B, Down
6 - Right, Up, Left, Up, Left, Right
Final - Down, Left, Up, A, Down, Right

Toe Jam:

2 - B, B, Left, Up, A, B
3 - Left, Left, Up, A, Right, Right
4 - Left, Left, Up, Left, A, Left
5 - Down, Up, Left, Down, Down, A
6 - B, B, B, Right, Right, Up
Final - Down, Left, Up, A, Down, Right

Twin Mill:

2 - Down, Left, B, B, Right, B
3 - Up, B, Down, Down, Right, Left
4 - Right, Up, Right, B, B, Right
5 - Right, Up, Right, Down, A, Right
6 - Right, Left, Up, A, Up, Down
Final - Down, Left, Up, A, Down, Right

Way Too Fast:

2 - Right, A, Right, B, Left, Down
3 - Down, Right, B, Right, Down, B
4 - Right, Right, Down, A, Down, A
5 - Up, A, A, Down, Left, Up
6 - Left, Up, A, B, B, Right
Final - Down, Left, Up, A, Down, Right