Dakota was correct, it was a rubber washer, not copper

 

Anybody have some known companies rebuilt diffs can be purchased. I see rebuilt diffs at British Atlantic... Trying to find all options

 

Rear locking diff replaced!

Wanted a rebuilt diff but could not find one... None in stock. Had to settle for a used one. This got expensive.... $2900 for parts and labor. Although the part was sourced prior to dropping off the LR3, shipping and repair took three weeks. The good news, it is AWSOME! Seeing the lights on the center and rear locks show on the screen was great, but the off road ability of this thing is far beyond expectations.

Now that I have repeated my vows to this '06 LR3, I need to figure how to fix the cracked dash... new thread