I have gone and put the wrong oil in my 2V Norge gearbox. Instead of the recommended 85w90, I put in the 80w90, which is specified for the final drive. Both Agip.
Any thoughts on whether this really matters for one 6000 mile change? Bearing in mind that the 80w90 is specified for both final drive and gearbox on my Le Mans (part of the reason I made the mistake)
Grateful if you avoid use of the “T” word in your responses!
Any T word in mind Jim? 
The 4 letter one ending in wat.
Jim
Usually preceded by “stupid…”
I’ve been using 80w/90 in my 1200 sport gearbox for some time now with no noticeable effects. I figured the viscosity difference between 80w/90 and 85w/90 was negligible.
Thanks. That’s what I was thinking. I have done a few hundred miles now and nothing noticeable, but would have thought if anything it would only be a long term effect. I will go back to the recommended at the next change though.
If the Specs are the same, other than the 80/85 difference, don’t worry.
I believe the difference in specified Oil composition for the Gearbox and Final Drive is something to do with a certain Metal used in one of them, which needs a certain additive to prevent corrosion.
One needs GL-4, the other GL-5.
Not sure on the details though.