I have a Yardman select series MTD model 13A0785t055 46 inch cut DOM 03/2011 ,mower moves slowly about slow walking speed,belts seem ok,my neighbor bought this mower new and it as always had this problem,he gave it to me and i checked the belts and pullys they seem ok,a repairman told me that alot of these come from the mfg about half full of oil in the hydrostatic transmission and i need to fill it on up with 40 or 50 weight oil but i can not find any place to add the oil,has anyone had this problem and whats the solution?