Weak direct rings could cause a no third but still have good reverse. Reverse uses higher pressure. How's the endplay? Is the direct drum riding where it's supposed to? Excessive clutch clearance could contribute to it too. Are you sure there is no scoring inside the direct drum where the rings ride? Absolutely no ridges whatsoever? Or a worn direct drum bushing, or pump journal where it rides. Can you wobble the drum? A wobbly drum will wear out the sides of the rings and they will lose tension.
