2002 Ford Expedition Banging noises from the front

When I drive on a rough surface and hit a bump, like a manhole cover with either tire, there is a knock somewhere around the tires. It only happens to one side unless the bump is long enough to reach both tires at the same time. I actually sounds like a shock has broken off and is banging against the spring but they are fine. I have changed the sway bar bushings but didnt help. The vehicle seems to have become a bit more "bouncy" since this has started. I have been told it may be the A-plate bushings. I have no idea how to check this. We are getting ready to go on a long trip so any help with this would be appreciated.