Test the value of the source:
JSlider source = (JSlider)e.getSource();
if (source == speedSlider) {
...
}
else if (source == gearSlider) {
...
}
Or add a specific listener to each slider, so that each listener is notified of the changes of just one slider:
speedSlider.addChangeListener(new ChangeListener() {
@Override
public void stateChanged(ChangeEvent e) {
...
}
});