Here's a follow-up. I went to work on pulling the subframe hook-up linkages apart this past Saturday. Turns out that all 4 of the swivel links were pretty well rusted onto the mounting pins. I went through a half a can of WD-40 just to get the linkages off (using a hammer to swivel them back and forth). One of the top swivels took almost 20 minutes of spraying and hammering the link back and forth before it finally came off the mounting pin. Once I had everything apart, I used the WD-40 and some wet-dry automotive sandpaper to get the pins and links cleaned up.
I put everything back together, and was able to actually swivel the linkages with my hands /forums/images/graemlins/shocked.gif. When I went to attach the backhoe to the tractor, I couldn't believe how easily it hooked itself up - even the spring loaded link pins just snapped into place when I pulled the lock pins - they had never done that before.
What used to be a 20 minute hook-up process with a hammer, now takes only 5 minutes when the linkages are functioning properly. /forums/images/graemlins/cool.gif We had been concerned with using an oil-type lubricant, as we figured it would attract too much dust and bind up the swivel links. But after getting them off, I realized that the fit is too tight to worry so much about dirt making it's way between the swivel link and its mounting pin.