63 valiant 904 push button trans removal help!

That cable actually runs a parking pawl, not a brake. It is held in place similar to the shift cable. There is a wire clip that snaps into a groove in the cable end. Go through the hole with the allen head plug like grimreaper said or if it won't come out use Dart6's procedure. Just be carefull you don't kink the cable or bend any of the retainer parts as they are getting a bit hard to find. It's usually the shift cable that's the harder one to get out!