From the Op's initial discription it seems that while the der will move far enough to shift into the large cog the lever won't engage a index "click" there. So either the cable is too loose, and when on the second from largest cog the lever is actually in the large cog position (as pierce said). Or the cable is too too tight and the lever wants a little bit more travel to engage the click. This should be an easy diagnosis for some one with experience. To repeate the question cny-bikeman asked, who set this up? Andy.