Serviced the Trimatic today.....
I've never seen so much black crap in the bottom of a trans pan in my life!
I was so surprised I didn't take a photo, but it was more than 1/8" thick... I don't think it had ever been serviced before.

I haven't driven it yet but it's certainly a lot crisper when changing from neutral to drive or reverse so I'm hopeful it's good.