After googling around a lot of sites, and a lot of " don´t use GL-5 " and also a lot of " it´s alright to use GL-5 " I found this site:
http://www.p1-performance.com/products/motul/gear_oils/motylgear_75W90( this is the oil I have at home )
Obviously it´s okay to use this one, so this weekend I´ll change engine oil ( to synthetic 5W-40 ) and gear oil to the GL-5 oil, maybe some cleaning of the machine, and then we´re ready for the snow :-) New tires are ordered, and hopefully I get them next week.
Regards / Thomas H