Black differential fluid

["Michael Cline" <mcline@c4.com>]

I read somewhere that the color of the transmission fluid and indicate what
condition it is in. My differential fluid in a 1971 TR-6 is black. There is
a good bit of play in it yet I am trying to put off a rebuild (it is quite
expensive). Does the black color of the fluid indicate that the is
something specific I should look for?

Mike Cline
1971 TR6
Denver, CO