Caution: Never perform any work on the screw jacks or associated transmission equipment until the prime travel length cannot be remotely or automatically started. Make sure the load is properly supported before the screw jacks, brake, or other holding devices are removed. Be sure the area around the screw jacks is relatively clean to prevent the parts from becoming contaminated, and the machined parts are stored on wooden blocks to prevent damage to the machined surfaces.

1. If possible remove the screw jacks from the structure and inspect the screw jacks on a work bench. If not use cribbing to support the load.
2. Clean the screw jacks of grease, dirt, and foreign material
3. Visually inspect the screw jacks for damage such as cracked, broken or chipped parts, and married surfaces.
4. Using a soft cloth or tape to protect the input shaft, with a pair of pliers or by hand, attempt to turn the input shaft. If it won't turn without extreme effort, total disassembly will be required. Consulting Jacton engineers for the disassembly procedure.
5. Measure the rotary backlash: Rig a positive stop and extend the load screw against the stop. Mark the position of the input shaft. Reverse the rotation of the input shaft until you feel the beginning of the load screw movement. Again mark the position of the input shaft. Measure the angle of this rotation. If the measurement exceeds the 60 degrees then the worm shaft and the worm gear must be replaced.
6. Measure the axial backlash: Extend the load screw against the positive stop. Mark and remove the positive stop. Protect the load screw with a soft cloth or tape, clamp a handle to the load screw and pull the load screw in the direction of the removed stop. Measure the movement to determine the axial movement. If the movement is greater then the allowable limits, the worm gear and the load screw should be replaced.