I don't like this sound...!
 

I am noticing a rapid thud-thud-thud-thud sound and vibration that happens sometimes when I start going up a hill after a stop sign, or when I accelerate a bit enthusiastically when the light turns green. As soon as it happens, I tend to back off on the gas and it goes away. I've tried goosing it when I'm already on the highway, but haven't had it happen at faster speeds.

It's a '96, 105K, automatic, with automatic stability control + traction.

Drive line Guibo?

Dave