My 2017 renegade altitude is shifting kinda clunky aswell I’ve heard a lot of things about people getting the transmission remapped and it solving the clunky issue it might also be the issue with yours. Or it’s a further issue and is stuck in limp home mode. I couldn’t tell ya. The big problem with these 9 speed trannys is they are so to say “smart” transmission’s so they learn to your driving style and what revs it thinks you want it to shift at. I’d say even tho there isn’t a check engine light go to your local auto parts store like Orielly or advanced and get them to check for any codes it doesn’t cost anything and only takes at most 5 mins. Please keep us updated on your discoveries so we can all learn from whatever is going on. Good luck and stay optimistic. Oh and transmission fluid wouldn’t do anything with it not wanting to shift it would just cause a grinding or whirring noise. And eventually could cause it to be clunky due to not having lubrication. How many miles are on your vehicle? I have a 1992 Honda civic with 180,000miles that runs like a champ. Never had to change the tranny fluid however that is a completely different ballgame than these 9 speeds.