A Ford engineer from the Wayne Plant in MI where the Ford Focus Electric is made talked to me yesterday at the Denver Auto Show.
I was surprised Ford sent actual factory people to our "usually not respected" auto show here! LOL
Anyway, he remembered the problem with our differentials, and did confirm that Magna, the supplier, simply failed to heat treat (harden) the pinon shaft (between the spider gears) properly. I should have talked to him longer, as it seems maybe a bit odd the 'cure' is to put on DLC coating instead of just proper heat treating processes. Whatever the case, I guess they want the assurance of the very solid DLC treatment to prevent any further problems.
Another Ford factory worker was at the Denver Auto Show, a very cute young lady who works on Mustang & Continentals at another Ford plant in MI. We walked around and she showed me what she did to put parts on the cars, a rare demonstration.
We all should visit the Wayne Ford plant for a tour before they change over to Ranger production. Most take a tour before April 2018 to catch the last Ford Focus Electrics coming off the line. After April 2018, no more. Ford is going to new models of electric cars. (Maybe the European Ford Focus Electric plant will continue on for a while, don't know for sure.)