Edited 11/11/23:
Checked the bolts again the other day. Top bolt loose. Bottom bolt tight as all get out. I had just tightened them both equally 10 days ago.
My theory is that one of the two caliper pistons was fully or partially seized, therefore putting uneven pressure on the rotor, which in turn caused the bolts to get out of torque. 20-year-old original calipers, showing some rust. Upon further inspection, that left rear rotor had warped slightly, possibly also due to uneven caliper pressure over time.
Solution: new rear rotors, calipers, and pads (on both sides), and a brake fluid change--all installed last night. Also installed new parking brake shoes and hardware while I was at it, which has made our parking brake functional again! Winning!
(original post and thread now follows, below)
+++++++
Hey all,
2003 Yukon Denali XL. 198K.
Heard a scratching/rubbing noise from the left rear wheel today.
Got home, removed the wheel to inspect. Got ready to remove the brake caliper and bracket, to inspect further. Then I noticed the two smaller bolts that tie together the caliper bracket and caliper WERE MISSING! Gone. Not just loose...they were not THERE. (All bolts on the right side were in place as usual.)
Went to Lowe's and got two M-8 1.25 25mm bolts to replace the missing parts.
Last time I worked on those brakes was one year ago. Zero problems since then. I have NEVER had this happen to any of our vehicles before.
I will likely never know what caused the bolts to disappear...but I am curious to hear your theories.
