i have a 1999 dodge cummins 3500 5 speed i replaced the head gasket last fall never got time to finish it due to remolding my house i just pulled it out of the drive way the shifter will go into 4 wheel drive but the front tires did not move with the rear tires if the 4 wheel drive electric activeted on the front axel or vacume i ask because i had the disconect some of the vacume lines to remove the head ort is it just because the truck sat for 7 months not sure where to start to figure it out never worked on a 4 wheel drive system with auto hubs ant info would be a big help