Today while getting some tires rotated on my 4104 the mechanic told me that two of my rear upper radius rod bracket bolts were missing. It appeared to me that they have been missing for years. I can only thank GM for insisting that the bracket use four bolts. They are huge 3/4"x4 1/2" grade eight bolts so they must take a heck of a force. They are also torqued to 400-425 lb-ft! I was pretty amazed at that much torque for bolts in shear.
The point being that you guys might want to check those bolts next time you are under your bus. I would never have believed that these bolts would ever loosen. I still don't know how it happened unless they were never tightened the last time the radius rods were rebuilt.
This time we used lock nuts instead of lock washers.