How To Back Off Automatic Slack Adjusters

Hi out there. I have a problem I thought some of your great minds might be able to assist with. Do you know how to back off automatic slack adjusters? I need to release them so I can loosen the brakes to remove the brake drums on a 93 Volvo semi. There is an arrow on the side that lines up with a notch and is held with a bolt on the top. There is a 7/16 nut to tighten the brakes, but it doesn't work going in the other direction to loosen them!

It should. Do you have an impact wrench? Keep in mind that if it's an Arvin Meritor product, the tightening and loosing procedures are the opposite of regular parts.