Much thanks to all of your replies!
I bought an Kenko PRO 300 AF DGX 1.4X teleconverter for my Canon 100-400L to use with my 60D. But the AF does only work manually! No automatic AF. I tried it on my 70-200, 100mm, and so on. but the AF does not work.
Even not on my wifes 7D.
Should I give it back? Or do I make something wrong?
With an f/2.8 or f/4 lens, it will be f/4 or f/5.6 with the TC, and that combo should AF on any body.