Problems with the parking brake on a 2001 F-350 usually stem from:
* Worn or stretched brake cables: This is the most common cause. The cables need to be replaced, not adjusted.
* Brake shoes worn thin: The shoes inside the rear drums need replacing.
* Problems with the parking brake lever mechanism: A broken or damaged part in the lever assembly within the cab can prevent proper engagement.
* Frozen or seized brake calipers/drums: Rust and corrosion can prevent proper release or engagement.
What you should do:
Instead of trying to adjust something that's likely not adjustable, take your F-350 to a qualified mechanic. They have the tools and expertise to diagnose the specific problem and make the necessary repairs, which likely involves replacing worn components. Attempting adjustments yourself without proper knowledge could worsen the situation.
Important Safety Note: A poorly functioning parking brake is a serious safety hazard. Don't drive the truck until the problem is properly addressed.