I tried this technique http://www.michaelfurtman.com/taping_the_pins.htm and it works to restore the AF on my 100-400 and 300 f/4.


It's a bit slow to AF, but it does settle down.


But, something that I didn't expect was the extender didn't affect the aperture setting.


The 100-400 still showed f/5.6 at its longest length and the 300 f/4 still showed f/4. I took a couple of shots from each lens and the file info confirms it.


I thought that this technique could over ride the AF, but I didn't think it would keep the aperture from changing to a smaller number.