What was updated on the 2018? I have a '17 and if its larger I'd sell OP my top cover with the charger if I can find one out of an 18. My phone is too big to fit.
I've got a 2017 6.2 with the 8-speed and 84K, no issues. It shifts a little on the firm side when cold but not harsh. No clue if the fluid has ever been done, but I will be doing it here shortly.