creaking in undercarriage?

when I hit a good bump at an angle and a bit of speed, causing the truck to rock side to side, I sometimes get some loud creaking that feels like it is directly underneath the front seats. any thoughts what it is? I have already torqued my u-bolts up to 68 ft lbs with no change. it doesn't seem to be a huge deal, but it is startling when it happens, and I plan to have Toyota take a look at it during my first scheduled oil change.

 

I get the same thing....plan on having it looked at with first oil change too.

 

If I have the windows rolled down and hit small bumps it sounds like I have jingle bells under the truck

 

this is pretty loud and...percussive, maybe? Windows up or down, it is very apparent. There is a dunkin donuts drive-thru in my town that has the perfect angle of approach to cause it, I'll try to remember to hit the video camera on my way in next time I grab a coffee to capture it.