Apologies if this has been reiterated in other posts, but just an fyi to others, if you are looking to prevent/eliminate the clicking sound, invest and install the traxxas center diff.
It will stop the ability to wheelie which is basically what causes the diff ring gear and pinion to strip. (And honestly, who continues to wheelie after they've stripped their first ring gear )
Even after shimming, I would still strip ring gears, but not a single one since I installed the center diff.
The trade off is I lose some mph with the diff, but its a fair tradeoff