My 2016 Yukon is suffering from the common transmission shudder issue as outlined in TSB 18-NA-355. My dealer states they can't get the fluid anywhere. I believe it is Mobil 1 Synthetic LV ATF HP. Amazon has it in stock. My plan is to simply buy it and bring it to them. What is the amount I would need to complete the flush? I imagine more than the stated capacity amount?