At first I thought I had a low tire because there was a light thwap sound coming from around the bronco and I was the only one on the road. As I got into my neighborhood there is a sharp turn and after that turn the thumping became very loud and started thumping against my left foot alongside the brake pedal. I stayed at around 15 mph, put it in neutral and revved the engine..the thumping did not change so it is not engine related. I don't think it is trans related and seems to be front left side. I was in 2H obviously with the hubs unlocked so I don't think it is front drive train. The thumping speeds up and slows down in relation to speed and the feeling under my left foot is same exact tempo as the audible thump. When I press the brakes hard enough the thumping seems to go away while the truck slows to a halt. Any suggestions other than use search?