46RH valve body lower plate
 

Found this going through the valve body.
Not sure why this would happen when I had a leaky heat exchanger.

Does anyone know where I can get a replacement? Nowhere on the internet I can find. I might have to buy core valve body I guess
https://cimg0.ibsrv.net/gimg/www.die...d0a6abb87b.jpg
https://cimg7.ibsrv.net/gimg/www.die...9a6079e0d8.jpg
https://cimg3.ibsrv.net/gimg/www.die...f1f29d4e4d.jpg

Looks like a replaceable part.

I did find one, thankfully!

I wonder if a pressure regulator valve got stuck.

Yes sir, upon further investigation, that's exactly what happened,
Found a tiny sliver of alum jabbing it up.
The front alum planet was a little chewed up, sending little pieces through out.

I was hoping I wouldn't need to replace my TQ, but now I'm too scared to put back in the old one.

Yeah. Those automagic things are kind of finicky about metal shards flowing around. I'm sure there could be some lingering in the TC that will give you problems down the road. A full disassemble/cleaning with a new TC would be in order. Or maybe just go get a rebuild or a good used unit.