Here is the info
The z axis jogs smoothly

With a .1 inch up and down loop it moves up .010-.012 inches in 100 cycles.

I have not tried swapping drivers because everything is hard wired.

computer: pentium 4 2.8 Ghz, 256 Mb of ram, windows XP PRO

Mach3 ver. 3.043.022

screen set: default

drivers: 2.4A, 31vdc, 1/8 step being used, bipolar(parallel) connections

BOB: Mechatronics 3 axis micro step driver

P.S.: HP ac/dc adapter #0957-2106, input 100-240 ac, Output 31vdc 2.420A