[SpitAndDirt]

the acuator may not engage with the truck standing still, you may have to try putting the whole truck on jacks and then trying it. Just be extra carefull, please!! The wheels need to move a little so that the actuator can engage properly. One other thing, you may have to have your computer read for fault codes that may not set a Check engine light. But may be stored in the Body Control Mondule or Transmission Control Module. You may have one or other other, both, or neither. Some GM's are getting real computer heavy nowadays. You might only need an update for that matter. Tell me how it goes -Chris