Jimwrench,
I understand your reluctance to take a very old working ratchet apart. Here's a couple of methods that don't require any disassembly:
1) You could just put a drop or two of 3-in1 oil, or machine oil, or gun oil, where the selector enters the ratchet head without opening the ratchet. Give the drive bit several spins, then shift directions and spin the other way several times. Done. Or,
2) You could try the JAFE method. Mix equal parts of acetone and power steering fluid in a jar and submerse the entire ratchet head in this mixture for 24 hours. Then take the ratchet out and give the ratchet a spin in both directions and resubmerge the ratchet for another 24 hours. After the second soak, spin the ratchet in both directions, and blow out the ratchet with compressed air the thru area where the selector enters the ratchet head. Done.
Both methods are easy and work well. And, you'll notice a big difference. Your choice.