I have a troy bilt 42" cut lawnmower, mdl 13AN77TG766, S/N 1B237B70301, DOM 2/2007. The transmission will not engage until I am in either 4th or 5th gear. These gears and above work just fine, but are too fast to mow with. I have pulled the double pulley, cleaned it and lube it with powder graphite, it had not effect. Occasionally when I spay belt conditioner on it, it will engage in 3rd gear but will soon stop. Is there any adjustment or repairs to fix this machine?