FYI... When I owned a Porsche 944 Turbo(way back when) many PCA guys used Swepco gear oils in the trans and diff's. The fluid was bight blue/green and was used mostly in the food industry. Many guys swear by this fluid for P-cars.
http://www.swepcousa.com/lubesite/gear.htm
I would still stick with using either OE fluids(for the trans and diff) or Redline AFT-D4 for the trans and Castrol SAF-XJ for the diff. And change them often (20K to 30K miles).