[dracozny]

What do you mean "backlash at the pulley"? Is it rotational backlash ie turns a few degrees before it moves? Have you checked the ballscrew shaft for movement under load (moves up / down when you apply a load)?

yea the shaft turns about 3 teeth from one extreme to the other with the gib locked down and about 80lbs of torque applied to the pulley. The ball screw does not move longitudinally my bearing mounts and preload are solid. As mentioned either my ball nut mount is warping or the slide is flexing.