The Klaxon wiper gearbox regularly suffers from damage to the worm wheel, originally made from a moulded fibre material, and excessive internal lost motion due to wear in all the linkages and pivots.
Be aware that the angular sweep of the wiper arms is dictated by the the 'throw' of the worm wheel. The longer the 'throw' the greater the sweep. Both gearboxes should have the same 'throw'. In addition there are variations in the mechanisms for parking the wipers when not in use.