Fluids for transmission/transfer case C4

[beckertb]

I am certain this has been covered in the past, but I purchased this past year a 964 C4. On most of my other previous vehicles, I have changed the transmission and transfer case (where applicable) fluids to synthetics. I did change the engine oil over to synthetics (car with 30k miles), but am not certain what synthetics are recommended for the tranny and transfer case. Anyone with insight? Many TIA. Ben.