so i binned my 5inch freestyle build pretty hard into a concrete pillar last week, classic moment of thinking i had more clearance than i did. snapped two props, bent a motor shaft on motor 3, and the frame cracked at one of the arm joints but its still ridgid enough that im not replacing it yet.

anyway i ordered replacement motors, same stator size and kv as what i was running (2306 2450kv), swapped the busted one out last night. resoldered the phase wires, checked rotation direction in betaflight, all looked fine. bound up, did a prop test on the bench and it sounds... off? like there's a slight rattle or hum on that motor that wasnt there before. its subtle but i can hear it compared to the other three.

i double checked the bell isnt loose and the prop nut is tight. the motor itself spins freely when i turn it by hand, no grittiness or anything. is this just like a break-in thing or should i be pulling it back off and checking my solder joints again? im wondering if maybe i nicked one of the windings when i was stripping the old wires but i dont really know how to check for that without proper equipment.

the hum/rattle thing on a new motor after a crash repair ? nine times out of ten in my experience its either a slightly loose prop adapter or the bell got a tiny dent from the impact you didnt notice. like even a small ding in the bell can cause vibration that you'll definitely hear on the bench. spin it up without a prop and see if the sound is still there, if it goes away then its a prop seating issue, if it stays then yeah something is up with the motor itself.

also worth running blackbox for a few seconds and looking at the gyro noise on that motor's axis. if you're getting weird spikes compared to the other motors it'll show up pretty clearly. i had a similar situation a few months back and turns out one of my phase wires had a partial break inside the insulation, looked totally fine visually but was causing intermittent issues. had to swap the whole motor in the end.

could just be the magnets are slightly off from the impact? i honestly dont know if that's a real thing or not but i feel like i read about it somewhere. probably just check your solder joints like you said, a cold joint on a phase wire can def cause weird behavior. also make sure the motor screws arent too long and touching the windings, that got me once and i felt like an idiot