Z motors sound bad only when homing?

I just finished (all but my extruder) building my prusa i3. Everything is running well except for z axis homing. It sounds terribly noisy. The odd thing is though, if I send say a G1 Z50 code from repetier it sounds just as one would expect and moves quite smoothly. I can use repetier to move it up and down in increments of .1, 1, or 10 mm and it s great.

If I tell Z to go home from repetier it sounds awful. The same thing happens even if I move a millimeter using the graphical LCD controller. I have a feeling this is some type of software issue since the Z axis works well when controlled with Repetier (exept when homing in repetier). What might the issue be? I am using Marlin with a standard Prusa i3 rework build.

Sounds like it's homing too fast. Drop the homing speed and you should be OK. Look under Config / Printer Settings / Printer and reduce the Z-Axis Feed Rate (100 mm/min should be OK).

Thanks. I dialed back almost all of the feedrate and acceleration parameters. It works just fine now. I was able to perform a dry run (still no extruder) and it prints just fine. I think it took 11 minutes for the printer to (think) it print the small wade gear. Have I dialed back too far, or is this pretty "normal" using 30% infil?