I just purchased a Case 970 Agri King that may have sat for a while without being used. I purchased it from an estate where the guy who owned it died and his wife did not know anything about the tractor. I have just started to work on the tractor and found that it is hard to shift into some of the gears, But after playing with it a little last night I was able to get it to shift into all of the gears except 4th or road gear, Where should I start trouble shooting, could it be a bent or improperly adjusted linkage? sticking valves, etc. or does this sound like a internal transmission problem? It acts like it drops into 4th gear, but I get nothing.