My tractor will start fine and run forever at idol but once I put it in forward it runs about 3-5 min and then automatically chokes itself out. I can start it back up right away but it immediately chokes out again. When it starts to die out I can give it ten more seconds by throttling it all the way down but then immediate stop when put in forward. Any ideas. Is there some kind of hydraulic pressure switch shutting me down maybe like a low oil cutoff. All help appreciated.