Thanks for the quick response. I did a sight inspeciton around the backing plates, but will look for more eveidence. I have had this truck for about 6 months, but haven't really gotten into inspecting everything. I was going to start on a wiring harness this week, but this is more pressing. I did see that my passenger backing plate has a pie shaped piece broken off. I'll be searching for one of those.

A day without laughter is a day wasted- Charlie Chaplin
When wrestling a grizzly bear, you have to keep at it until the bear gets tired, not when you get tired.
1948 Chevy 2-Ton