Mine was the same as Velojet:
Windows 7 - Firefox Nightly
Gamepad 0 ID: 46d-c216-Logitech Dual Action
The Y axis of the right joystick is in Axis 5. I had to modify the following line in the Gamepad plugin's runtime file, to have the Y right axis work with my Logitech in Firefox Nightly:
var win_ff_lda_axes = [0, 1, 2, 3, [14, 15], 3, 3]; //the last element is now 3, which means the raw axis 5 should be translated to right axis Y