How to fix the rattling noise on a 2006 honda civic 1.8 s automatic transmission?

Time to change the transmission fluid?

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-14.html#post2634481

My car is making a very loud rattling noise especially when driving slow and when parked with engine on. What could be causing it? How to resolve this problem?