I was poking about on the interballz a while back, researching Penrite oil for my D2 auto. I stumbled upon a thread on the FordPerformance forums where a bloke had done a change in his 6 speed auto falcon turbo from OEM oil to "something else", changes were rubbish, he then flushed and serviced and filled with a Gulf Western Product and trans operation went back to normal.
Funnily enough, I was at Auto Trans Services earlier in the week, pricing a service on the aformentioned disco and he uses exclusivly Gulf Western, I did also question him on the geniune ZF oil but he soley uses the GW now.

