Season the chuck roast with salt and pepper on all sides.
In a large skillet over medium-high heat, melt the butter. Add the roast and sear on all sides until browned, about 2-3 minutes per side.
Transfer the roast to the slow cooker.
Add beef broth, brown gravy mix, ranch seasoning, diced onion, and garlic. Stir gently to combine. Cover and cook on HIGH for 4-5 hours or LOW for 8-10 hours, until the beef is fall-apart tender.
Remove the roast, shred it with two forks, and discard any large pieces of fat.
Return the shredded beef to the slow cooker and stir.
Turn the slow cooker to HIGH.
Add the dry egg noodles and stir to combine. Cover and cook for 15–20 minutes, stirring occasionally, until the noodles are tender and the sauce has thickened.