I have a sudden and violent shudder/shake when braking. It just started with no warning and shakes the entire truck. Relatively sure it is coming from the rear end. I have pulled the wheels and and cannot get any play/movement in the axles, but do have a little play in the rear u-joint. It doesn't seem like enough to cause the vibration. I will replace it anyway, but there is absolutely no vibration under acceleration, which is what I am used to with a bad u-joint. Would a brake drum suddenly warp and cause this without warning? Any other suggestions?

A drum shouldnt just warp suddenly but they will crack. Either way pull the drums and check, get them turned to make them true while they are off.

Thanks...I am going to have that done because it has been a while since thye were checked...but I have been nudged in a different direction now. It may be that the torque converter is not coming out of lockup. Anyone know how to diagnose that issue?

Latest question...would a locked converter cause a shudder during braking when the transmission is in neutral?

when mine had a shudder, it was from the rear brake rotor. You say it cant warped suddenly but hot brakes and hitting a cold water puddle can do it. My shudder went away with a new rotor.

Thanks Meeko. I feel like I have sufficiently chased my tail right back to the brakes. Time to pull some wheels...again.