As I’ve said, the gearbox drain plug was attached to the gearbox with a lump of epoxy filler. This was because the thread had been stripped in the hole which it was supposed to screw into. I drained the remaining gearbox oil, rinsed out the gearbox with a solvent, and removed the lump of epoxy. This exposed the drain hole, and I decided that the solution would be to effect a ‘Helicoil’ repair. This involves drilling out the hole and cutting an oversized thread into which the Helicoil repair can be inserted (it’s screwed in, and then the tang that gives you purchase to do the screwing is snapped off. I was a little worried about what would happen to the drilling and thread-cutting swarf, but I reckoned that the risk was worth taking; firstly, I could ‘catch’ the debris with a lump of grease and then clean that away, and secondly that the gear wheels would be steel and so much harder than the alloy swarf. Anyway, I carefully drilled, tapped, fitted the Helicoil insert, and cleaned again, before re-fitting the drain plug. I’m happy to report that the gearbox is now refilled and is oil-tight again. I’m sorry – there’s no photo here. I didn’t generally take pictures of my work.