yes you are right...should be each washer behind the small spider gear..
Did you have the washer inside for the out drive where the pin go in before the big spider gear?
I also believe the washers protect the metal gear from rubbing againt the plastic gear case...
I didn't use the washers when I built mine, I didn't see it in the instructions, and when I tried using them it seemed like it pushed the satellite gears too far into the main gear and the mesh was too tight. I just figured it was when the gears wear out and the mesh gets loose. I know that's how some/most 1/8 scale buggy diffs are, they come with shims to compensate for wear of the gears. I guess we will see if I did the right thing when I run it.
Does anyone know if they make plastic replacement gears, or a diff with 4 satellite gears?