Th400 Slipping in 1st gear... and whining...

[73CheyenneSuper20]

Background: It's a '73 C20 454 with a TH400 trans, not a daily driver, more of a weekend driver/ project.

What it's doing: It has started slipping in 1st gear, and has gotten worse every time I'm driving it. I drove it tonight and it really doesn't want to go in 1st, but once it shifts, it seemed to be ok in 2nd and 3rd. It also has a highpitched whine that goes with it, it whines regardless of being in a gear, neutral or park. I haven't noticed if it whines in reverse. Because it whines in park or gear, I think it's torque converter related. The whine has been there before the slipping, and was barely noticeable and then has just gotten louder.

Whats been done: Fluid level seems good, doesn't smell burnt and isn't black. I added a can of TransX and nothing happened. I added a quart of trans fluid and it got worse and started leaking. (The dipstick is chrome and kinda funky, it might not be accurate) I've been looking at other threads on here, but haven't found anything like whats happening to me. Have found a lot of other interesting info though.

What do you guys think? What is it? If/ can a torque converter go bad, what happens? Should I rebuild the trans? If I do, should I get a new converter? (Low budget)

Thanks in advance!