I have just recently went to the snow in my truck to find that my four wheel drive would not work properly. Now it would work on an occasion just fine with no problems but some times not at all or for a short time. So i looked in to it and all the vacuum lines seem to be ok. any ideas?

 

First guess would be the actuator... They are not the most reliable part ever built. Not sure how to check one though.

I'll make TXdiesel007's post for him... "Posi-Lok it and forget it!"
The Posi-Lok kit is a nice upgrade if the actuator is bad.