Ok, I will first start off by saying, I did NOT write this, nor did I even take part in helping to write this. This was a write up done by another member from a different forum who will take all the credit. Please do not credit me for this as I'm posting this for informational purposes only. That being said:
We need to offer correct information for people on this forum who are in search of learning about this car.
On to the information..
1) The F35 (SS/SC) does take a 75W-90, GL-4, transmission fluid.
2) You DO NOT, I cannot make this any clearer, DO NOT, want friction modifiers! The friction modifiers will not allow the synchronizers in the transmission to work properly. This goes for BOTH the SS/SC and the SS/TC.
3) As for the limited-slip.. Ours are sealed. They are "Quaife ATB" differentials, and the lubricant does not affect them. AT ALL! This is why you DO NOT need limited-slip additives! This goes for BOTH the SS/SC and the SS/TC.
3a) *Side note* - This is why the How-To, (On this forum), is incorrect. The OP used 75W-90, WITH limited-slip additives. He is throwing differential gear fluid, in his transmission. The fluid is too slippery for proper synchronizer operation.
4) Even though the F35 comes with GL-4, you might want to use an aftermarket GL-5, if you feel need be. You can, although, make sure it is the correct specs as mentioned above! MOST GL-5's meet or exceed GL-4 specs.
5) The F35, (SS/SC) transmission, comes with fluid part number 21018899.. While The F35, (SS/TC) transmission, comes with fluid part number 88862472.
6) SS/TC guys, I would ABSOLUTELY NOT run anything other than part number 88862472, this is the most current GM fluid for your transmission.
7) SS/SC guys, feel free to use part number 88862472, in fact, I HIGHLY recommend it. It is a 75W-85 GL-4. It is the new "standard", over the old 21018899.
8 ) IF you feel the need to go aftermarket on the fluid, the ONLY fluid I recommend is - Red-Line 75W-90 NS GL-5 Gear Oil, and I ONLY recommend it for the SS/SC guys. You NEED 75W-90 NS, if you plan on using this fluid, because there is regular 75W-90, which has friction modifiers. It does not matter if you have G85 or not. Like I said earlier, our limited-slip is a sealed unit. No fluid you put in there, will see it.
9) DO NOT use Royal Purple, or any of that synchromesh garbage. Either stick with the 2 factory numbers I provided, or the Red-Line fluid. NO IF'S AND'S OR BUT'S!!
10) The transmission fluid should be changed around, in my opinion, 60k. As for the amount, you will need to buy 2 quarts. However, it will only take 1.7 quarts.
11) The code for the SS/SC transmission is F35-MC2. The code for the SS/TC transmission is F35-MU3.