Shaking in the steering wheel when braking, but only on highway
 

Hi everyone! So I've had a car with warped rotors before. But the shaking didn't ONLY happen when I was braking at high speeds. So I was wondering what, if anything else I should suggest to the mechanic before letting them go at the rotors. I'm bringing it in on Thursday afternoon.

Side story, I just moved out here so I'm going to a totally new mechanic. Google has them at a 4.9 stars out of 5 with 35 reviews, best rated in the area... So I'm hoping I can go in there with a small list of specific possibilities for him. God knows I don't want to spend a few hundred replacing the rotors if that's not the issue.

There are lots of threads here about pulsating brakes on HHRs and the causes/fixes. In my experience rotors don't warp, the pads get hard and bake deposits onto the rotor thereby causing the pulsating. The tell is when you see little "comet trails" on your rotors.

All that said it's also possible you have a worn outer tie-rod.

I'm reading that the tie-rod would shake my wheel while accelerating, and that's not what's happening.

Nope it will do it when you are braking, especially at freeway speeds. Had this happen more times than I can remember on various vehicles over the years. If it does it while accelerating the tie rod is ready to break.

Rear drums, worn or in need of adjustment.

ANYTHING that is loose or worn out in the steering components could cause that vibration. LCA bushings , tie rods, steering shaft, etc. Any component that can give you "play" or looseness is suspect.
Have your new mechanic check everything steering related.

This post has just about everything you need. Do NOT point him toward the front brakes. He will probably lean that way to start. If you have rear drum brakes, the adjusters may be (often are) stuck and shoes no longer contacting the drum. If this is the case, all the braking is being done by the fronts. They could have overheated. He needs to check for loose components AND rear brake adjustment. Cleaning or turning (and, in severe cases) replacing front rotors may be necessary. If they have been overheated, there is going to be uneven pad material deposited. That causes pulsation. Just don't simply replace the fronts, and complain if it returns. The cause could be the rears dong nothing.

Chassis warranty guy at another OEM...

Would anything related to the shake possibly involve the dreading clunking noise? In the past 3 years, I've had my sway bar bushings replaced twice because of that noise. It came back recently, and the shaking also just started recently.

​​​​​​So far, I'm mentally jotting down LCA bushings, tie rod (well, I'll just say check everything steering related), and rear drums.