Originally Posted by Tony Vega
My kit was missing this washer too. Do you not need to use it? I ordered replacements from CRC but are the Associated ones the same?
The black belleville washer is the "spring" to keep your diff setting consistent. Without it you are relying on the plastic locknut to not deform or move. One locknuts, it's not a problem but when they get old, they need help (or a new nut if you're a high roller<g>). You can probably get away without it but we have been using these in 1/12 scale diffs for almost as long as I can remember. I personally have always run with one.
BTW, the AE one should fit just the same and be easier to get locally.