Stuart Firth
The way I see it is that as long as you are absolutely sure the motor/gearbox are running smoothly before you install them then the driving axle is unlikely to give you any trouble. If the gear wheel has a grubscrew fitting then the worse that’ll ever need to happen is you’ll have to remove one wheel to enable you to draw out the axle and free the gearbox. Re-fitting it may need Loctite though the tightness of fit of Gibsons varies enormously, from quite loose to needing a vice to put them on. I have had them off and on again occasionally on one or 2 loco’s and it’s never been terminal (yet!) Of course there’s always Markits…