installed new brake light switch onA833

Well I've never had an 18 spline input, so I'can't speak to that.
But I did notice that on the 23 spline regular trans,
And a 340 disc, and old Zoom 3400# 3-finger B&B pressure plate
and 185psi cylinder pressure;
My 367 kept spitting out the springs, because they smashed the retaining plates up. After I switched to a CenterForce this problem went away. But now, I had a bit of rattle at very low idle...... which I attributed to the strong power pulses of the cam, at 185psi, that the springs were transmitting straight into the cluster gear..
So, I'm guessing your disc springs are doing the same thing, namely transmitting the power pulses into the cluster gear.
I found that CFII disc Too good,if you can imagine that. It busted a lot of parts behind it, and eventually I went back to a 340 disc,and eventually learned to be a little nicer to it.
I'm pretty sure the high cylinder pressure and a bit of a lopey idle, caused the rattle. That 270/276/110cam was in there for about 4 years. The next cam was a 276/286/110, so the lope was a bit more,but the 340 disc is handling it, altho I'm on the third one,in the CF. Hyup, still spitting out springs and tearing off the linings. I haven't actually worn one out yet. The CF pressure plate is still looking real good tho,lol.
And that's why I asked about cylinder pressure. My stock Low-C 318 bolted up to all the same parts never rattled, with its modest 140psi