The cooper ring surface, where the brushes ride on the shaft has worn down to nothing.
All this after 300k miles, 4 or 5 sets of brushes, 1 voltage regulator, a set of bearings, and lots of mud.
The alternator shop wants to sell me a rotor, like the one below,for $45.
If I could just replace the slip rings or maybe its not that easy.

I pulled the photo below from Toyota Nation's forum.
From this write up Rebuild your own alternator. My camera is not good for close ups
...anyway you can see where the brushes ride on the cooper slip rings.


[Linked Image][Linked Image]

1991 FJ 80 Land Cruiser for fun.
1998 GS300 for the wife
1998 GS400 for me
1991 Supra SOLD
1986 4Runner 335k miles-22re EB inside.SOLD