Does anyone know the mechanical construction of the centre diff? By the comments from Ogier the Ford is rear wheel drive without hydraulic pressure.

https://www.ewrc-results.com/driver_...-de-Corse-2017

SS8 Novella 2: "At the end of SS7 we lost hydraulic pressure. The target was to finish the day and be back at the service. We don't have any diff, no gear shifting and we're a proper rear-wheel-drive car. It behaved quite strangely!"
On SS9 Antisanti – Poggio di Nazza he had electrical problem and the centre diff was locked which mean he had hydraulic pressure. Looks like the electric control system was an on/off system on SS8 and SS9.