Clone prusa z-axis rate and steps issue.

Greetings. I am a novice. Just built first 3axis prusa clone Reprapguru brand

Having trouble with z-axis trabel and rate of travel.

Homing works, print starts, extrusion looks good. The layers start smashing together.
So z-axis travel is not set correctly.

However if I set default z-axis travel to calculated value for threaded rod, 25600, the motor just screams during homing.

Please direct me to guidance on related issues. I have been and continue to search the Marlin firmware forum.
Thanks!

I do not know what 25600 represents, but I have never seen a number that high for anything. You may want to try a different calculator.
Mine is a coreXY so the numbers won't relate but.....maybe it will give you a clue if this is what you are referring to;

#define DEFAULT_AXIS_STEPS_PER_UNIT { 200, 200, 800, 176.0 }