2013 550 xp, was hard to shift from new. I use Mopar atf+ 4, and motorkote hyper lubricant , Shifts like butter trans stays cool.
Also use in rear diff and engine. Rear diff was always very warm. Now with aditive stays cooler to touch .
I found ATF+4 to be the best after many other fluid trials. And even without motorkote, was slick shift.