Okay, some thoughts (I have an '84, too, by the way, but it's only got 220K miles).

First, re: "...Thought maybe bad electrics somewhere so I disconnected the solenoid and no solution...."

That won't help. The AW70/71 defaults to a 3-speed when the overdrive control system doesn't work, so disconnecting the electric wires to the solenoid would certainly keep the tranny from shifting up to 4th/OD (even if the system was good).

Second, you need to tell us:
1) when you use the button, do you hear a clicking sound? That should be the overdrive relay (just behind the center vents, accessible by removing the glove box) working. It would be suspect if you don't hear it click.
2) when you use the button, will the dash light illuminate?

If none of these things (sound, light) happen, then you may have a bad relay (as I explained above, that's a lot easier to get to then the solenoid, and should have been your first suspect); or you may have a bad wire in the shifter (22 years of moving the shifter back and forth can wear insulation and break the litte wires within); or you may have a bad pushbutton (it's a momentary-on type of button). These things you can all test with a VOM. The last thing you should suspect is the solenoid.

I have to say that I would never have given the tranny a sea-foam treatment -- at best, you should have just done an ordinary flush with fresh ATF (Dexron).

Anyway, get back to us with your answers and we'll continue to try to help you diagnose this.

Good luck.