I have a 1994 mack triaxle dump truck,350 engine,8LL transmission,been sitting a little while, tryed to move but not getting air to brake valve on dash any ideas what I might check would be thankful,looks like a few air lines have been messed with under dash, when I do supply air to air valve from another souce, transmission only goes into high, before it was stuck in netual.I could use some kind of air diagram,any help I would certainly be thankful;

Truck was fine when parked. Thanks Rick