Horrible Stepper motor grinding when auto bed level is enabled

[Butt_blaster]

For posterity:

It was a setting in vanilla marlin.

Follow this guide and you should be ok:

https://www.reddit.com/r/ender3/comm...r_mini_e3_v12/

Specifically I think it was the electrical current settings in configuration_adv. The defaults set the max current to a full amp, which is a hefty chunk of current for such a small chip as the stepper drivers. I believe the stepper drivers have built in overheating/overcurrent protection that shuts them down when triggered, but doesn't alert the firmware by default, so the awful grinding was that protection constantly triggering and un-triggering. The guide recommends 560mA, that's where I have mine now and it's working just fine.

EDIT:
SCRATCH THAT, SCRATCH ALL OF THAT

Those are the words of the stupidest person alive. My Z acceleration was set to zero. I don't understand why that was the case. I don't fully understand why setting z acceleration to be non-zero would make any difference, but it did. Who cares. If you have this problem, check your z acceleration.