I have a 2002 Chevy Cavalier with 130k. I’ve noticed when I press firmly and/or suddenly on the brakes, when I release them, there’s an audible thunk and sometimes a lurch from the back. What is this?
Sounds like the drum brakes in the rear are sticking, and then suddenly releasing. Or you may even have loose parts in the brakes.
If you can do your own work, take the drums off, and make sure the drums and shoes are still within specs. If not, replace the shoes and resurface the drums.
If the stuff is still in specs, then use some brake cleaner and get all the rust and gunk out of the area, then some bearing/axle grease on the contact points where the shoes slide.
Also, make sure the pistons in the brake drums move smoothly. But do this carefully… if you press on the brakes while the drums are off, you could shoot the pistons out of the cylinders!