I hear the forums are buzzing with “expert” advice on Commando gear oil. The rumour is that GL5spec 80/90 or 90wt extreme pressure gear oil will damage the bushes in Norton gear boxes. We have been selling BelRay 80/90 GL5 for years to Norton owners and are not aware of any problem so I referred the matter to the most experienced Norton mechanic I know of in the UK.
Here’s his reply:
“It’s a load of rubbish. I have stripped and rebuilt many hundreds of Sturmey
Archer dolls head, upright, laydown, AMC and both types of lightweight twin
gearboxes and always use 90 or 80/90 oil without ANY problems.”