What is the purpose of the "speed change interlock"? My 1986 L2250DT speed change works fine as does everything else but there is an adjustable rod underneath the tractor that is disconnected from the actual speed change lever. It should be connected via a "pin" made on the bottom of the lever that should be connected into the adjustable rod with a cotter pin. The "pin" is broken off. The tractor operates fine when changing from hi to lo speed and lo to hi as it should. With everything working as it should, just wondering what it is needed for??? It makes a lot better sense if you are able to see it on a parts list etc.. Thanks