3208 cat turbo, starts but will not shift into gear

Thanks for all the replys; I thought transmission fluid was a problem but filled it up because it was low, but no go. Transmission is an Allison 1989 variety. Am going to check fuses next. Dont think idle is a problem but will look at that right away. When I finally get it figured out and back home, I will let everyone know how it went right after I have a Bourbon in my favorite chair. Well not "in" my chair but in a glass while I am sitting in my chair :-)