So, I rounded out my TC collection today by adding a TC-14EIII. Put it on my 300mm f/4.0 AF-S. Get FEE message. Dismount and remount. Same message (on D800 body). So, I go try a D600 body. Same results. I put on a TC-20EIII, everything works fine. Go back to the TC-14EIII get FEE. Grab a 70-200 f/2.8 AF-s VRII. The TC-14EIII works just fine. Put the 300mm f/4.0 AF-S on, FEE!!! Open the box and pull out the 400mm f/2.8 AF-S. Put it on, FEE!!! Get on Nikon's site, only lists current lenses as being compatible. And the 300mm f/4.0 AF-S is not on the list. Neither is the 400 f/2.8 AF-S. So, I do a web search and sure enough there is a list of my 400mm and 300mm as not compatable. And yet the TC-20EIII IS! My TC-17EII is. Apparently if I want to have a 1.4x TC I have to buy the older TC-14EII! So they make the 20 compatable with older lenses. But not the 14??