Thanks for posting that list Alan. I've seen it before but didn't know if it was accurate for the later years. I just uncovered two yellow marks on the bottom so it looks like that chart still applies in 73.
After getting most of the grease off the carrier not much was visable. I had some old almost used up EvapoRust so I thought I see if it would do anything. I'm amazed that the marks were still there under the rust. Here's what I found.
orange mark on top...I can't tell if the flat pad is painted black or if it's just dark rust.
two yellow marks on the bottom (2.76 gear)
This is all I could see after cleaning the grease off the side.
After soaking in EvapoRust.(it looks like 10Y with a 7 above it)
