8V Gearbox

[Bobolink]

Can anyone tell me about the 8V gearboxes?  I'm assuming it's a constant mesh type.  Also, are there any copper alloy metals in the gearbox?  My 2013 Norge manual specifies a GL-4 gear oil.  It's my understanding that GL-4 was intended for transmissions that contain bronze synchros or bushings.  It's also my understanding that modern GL-5 oils (those of the last 15 years) use a buffered sulfur that is not corrosive to copper alloys. 
I'm just curious as to why Moto Guzzi specs a GL-4.

Thanks

[canuguzzi]

Just a guess but maybe it's a holdover spec, like other docs, no need to update it because it worked in the past?

[pauldaytona]

this is the spec:
http://travel.eni.com/catalog/products/documents/001423_1_en_IT_1_106.pdf

gl-4