email (option): peterroebuck@aol.com

While these questions are being asked is the manual saying that the gearbox requires 85w/90 SAE oil and the engine should ideally have 10w/50.

email (option): 79Aust@sky.com

Use SAE 40 engine oil everywhere..(gearbox, primary and engine.) Under no circumstances should you use modern hypoid gearbox oils as they can damage the bronze bushes...Change the engine oil to 50 if we ever have a hot summer
...I use Morris's SAE40...Alternatively a good quality 20/50 multigrade will work as a second choice...Ian

email (option): ian@wright52.plus.com

In Australia I run penrite 50 grade[I think it is really a 50/70grade]in the motor.In the gear box I would run the same if it had a seaded main bearing,it does`nt so I use a liguid grease other wise it just leak`s to much,I have done this on most of the old bikes I have owned, yet to have a problem, but I do`nt do any racing gear changes

What you put in is no where near as important as how often you replace it.
I use 20W50 in every thing as I buy it in 44 gallon drums.
As for the box most modern oil will be OK you just need to check that they are recommended for syncromesh gearboxes.
Thicker oil will leak less.

email (option): wariron@tpg.com.au