With 12v at the transmission, it should be locking up in 4th gear Assuming you have the kit in there that will automatically lock it up once in 4th. As I understand it, it just controls the 4th gear oem solenoid.
So, if you have 12v going "to" the transmission then either the converter is broken and won't lockup, the lockup solenoid is bad or you have a issue with the lockup "kit" that is installed in the pan.
Next step will be to drop the pan and see if that 12v make it "into" the trans and all the way to the lockup solenoid. If it does, your down to the solenoid or the converter itself.
But... back to your last post....
If you getting 12v at pin 85 (and assuming 86 is ground) then it does indeed think your hitting the brakes. You have a short somewhere or there is more to your circuit than the single relay.
With power on pin 85, pin 87a should not have 12v since 87a is the normally closed switch which will open when power is put to pin 85). Pin 30 is the switched power that is interupted when pin 85 gets power...
So, What you said your seeing doesn't make sense. If power is on pin 85, there should not be power on pin 87a which means there should not be power at the trans. On top of that.. If you do have 12v going into the trans then the transmission should be locking up. We must be missing something here since those two things (power on pin 85 and power at the trans) are mutually exclusive.
~Mark