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You surely do not think that there is not a diff? Without it it would run/turn like an an oxen cart.
It is called a transaxle - transmission and axle (yes with a diff) mounted in front of the flat6. Below a photo of a 997 GT3 transaxle (PDK similar). The tranny is on the left side, followed by the diff/axle (right of center) and the clutch bell housing on the right:
While not necessarily a PDK issue, the fluid used in a transaxle has some unique challenges.
Differential fluid, like in the pumpkin in most cars, requires Delvac (usually), a thicker and G5 rated oil (for track and GT3 use by Porsche). Gears in a manual transmission require a lighter and G4 oil. My manual prescribes Mobilube PTX, a G4.5 rated oil showing a mid-point. (Finding any oil that G4.5 rated is like finding hen's teeth btw.)
Regarding "sliperyness", differentials require sliperyness to not wear given the loads they transfer, while manual transmissions have friction modifiers to actually allow the dog gears to grab and spin up the transmission when shifting. Manual transmissions are not good with super slippery oil. Further, there are additives and such to protect the different metals used in each of these technologies.
So... what does this all mean? .... well first, I need to put my Kevlar on because I am about to unleash the monster in many netizens....... here we go.... gotta prepare....... ----- follow what your manual recommends and you will be OK. The engineers have worked hard to get these formulations correct. Add to this the fact that your PDK, according to Porsche, is a non-serviceable item and has to be completely replaced if there is a problem.... a very expensive proposition.
Thanks for the clarification. I was getting confuse between diff and transaxle. As there was no reference to rear diff oil change.
A PDK uses 2 types of oil - clutch oil and gear oil. The gear oil lubricates the gears and diff. No friction modifiers are used if the diff has an LSD. ONLY use OEM products, no substitutes.
You should know that the clutch oil requires a specific procedure under a certain temperature and PIWIS control.