we have a 2004 Sienna LE.
I noticed it shuddering when braking so last month I changed rotors. That eliminated the shuddering, but now the darn thing squeals when the brakes are applied. I just did the pads about a year ago, and there's still a lot of material left on the pads.
I was very careful not to drop any shims when I moved the calipers to do the rotors, and torqued everything back down according to the book. don't know how I made this happen...