Welcome to the Wide World of Trucks! Yes that is an OEM trans mounted parking brake. The nut on the bottom is 1st adjustment, wear compensation adjustment should be done at the handle, clock wise tightens the band.
Note- the bottom adjustment should be done only after the handle adjustment is backed all the way off.
Scrape the big stuff 1st then find some one with a real steam cleaner & offer to "Rent" it for a few min. Caution!!! You may wash off something that is holding the lubricant in!!
Don't ask how I know that...
