In what way is it friction shifting ? If you mean that there is no distinct click on each gear position.

Maybe there is some old grease that clogs up the ratchet mechanism. Shift the gear to the smallest cogs and remove the gear cables, and using the little tube that comes with the WD-40, squirt the insides of the shifters to dilute the old grease, followed by a few blasts of compressed air that will clear the gunk that is sticking in there. You should be able to get positive clicks from each gear shifts.