Freightliner Columbia '08 Eaton 10 speed Range Selector ( splitter) issue

I have a '08 Columbia with a Eaton 10 speed manuel transmission and I'm having problems with the range selector ( splitter) , sometimes in the morning i cant switch from low to high. The first time i was told ( from the mechanic in my yard that some valve was stuck in the box and he just spray it ) and then everything was fine for two days. Than it happen again. I didnt drove that day( I drive local) and decided the next morning to take the truck to a dealership ( the mechanic that unstuck that valve was off for two days) and then the truck was working perfectly fine so I didnt... I was told that the cold weather (Chicago) might cause that problem but i realy dont know what to think. Any suggestion would help... Thanks