[emanuelxcars]

As the title states I am having some issues filling up my ZF8 transmission after the service. I ordered the ZF pan and lifeguard 8 fluid from FCP and followed all their steps to a T. The car drives fine in comfort and shifts are perfect and silent in comfort and sport+ no matter how hard I accelerate. (N55 MHD Stage 2+ 70k miles)

My issue starts once the transmission reaches 75C, because that's when accelerating hard in gear 1 and 2 create a very loud supercharger like whine. From what I've been reading, at 75C the thermostat for the oil cooler opens up.

I know that they mention to overfill the transmission by 0.5L when doing the initial fill but I find that very hard to do because the more I fill it the more liquid drips out. It's almost impossible to overfill it. I was wondering if there is any tool or grommet that can be put in the fill hole to allow for that additional 0.5L to be added on... or do I have to just keep pumping the fluid in faster than it's coming out and then quickly put the fill plug on.

Realistically even after driving it, letting the trans reach 75C so the valve can open and then letting car cool off... the valve would still be open after I shut off the car since it is above the 75C threshold and the fluid would drain back into the pan, in turn not letting me overfill.

Is this just bad design or am I missing something? Is it normal for the gearbox to make those noises especially only after the trans reaches 75C (possibly confirming my suspicion about low fluid).