Well, technically not a spanner… a 5/32 allen key. Whilst installing the overdrive, I managed to drop the allen key used to tighten the 3 grub screws on the new coupling. It slid out of site down to the lowest part of the transfer box.
One solution would be to removed the sump plate and extract it from beneath… drain the oil, remove the sump, trash the gasket, clean off all the old sealant, wait 2 weeks for a new gaskets and refit…. all the while with EP90 dripping out of the bottomless gearbox.
Another solution would be to extract it from the top using a magnet on a length of fencing wire…. but pretty sure that wouldn’t work as the fencing wire would not be rigid enough….Turns out there’s a proper tool out there and my TD5 Defender owner colleague kindly leant me his. (The tool, not the Defender)
Refit cover plate, remove gaffer tape, open beer… in that order 🙂