I'll try to hijack this one so I don't make a whole new thread. Mine's an automatic too, started making a rattle at a specific point. It's best to replicate it by a cold start, put it in D or R, hold the brakes and get the RPM to around 900, very narrow band I'd say 850 to 950 right at the biting point? Can hear it when starting slowly from a stand still but only for a fist minute or so. After I drive off and thing start getting warm it completely disappears until it gets cold again after I finish work or in the morning. When I try to replicate it while the car is warm I cannot hear anything. I'm not even sure if it's something vibrating or grinding
https://www.youtube.com/shorts/v-w9pgSzg_0