Here are all of the pieces inside the joystick on the bottom row.

1 - The sensor that causes drift when dirty

2 - The bottom part of the joystick that the stick fits into. This is what moves the sensor left/right.

3 - This piece sits on top of #2. This is what moves the sensor up/down

4 - The stick. This fits through the hole in #3 and fits inside #2.

5 - These two pieces are what make contact with the sensor and they are moved around by #2 and #3

MISSING FROM PICTURE - There is a little black plastic piece that is in the shape of an arch that locks #2 into place in the housing.