My 2007 4Runner started making a "Thunk" noise every time it hit a bump. It had the original struts and shocks on it so I replaced with some Bilstiens. The thunk was still there. I randomly came across a video on youtube with a guy with the same problem. He replaced his front end sway bar bushings and fixed it.

I just replaced mine, which were apparently the originals after 167,000 miles. Its only a four bolt job but dang... it took me an hour with an 18 inch breaker bar to remove the 4 bolts. I spent 14 dollars at AutoZone for new bushings and the truck sounds completely different.

I did some searching on this forum and did not find this answer to my problem. Hopefully this helps someone out.