Well, the shuddering has gone away...here's what happened:

For several weeks, I've felt a strange vibration/shudder in my drivetrain whenever I let off the gas. It felt kind of like my engine was missing on a couple of cylinders, but it seemed like the shudder itself was coming from somewhere between the engine and the rear diff.

The shudder was worse sometimes than other, but a few days ago it really started getting bad--to the point that passengers were making comments. I just about made an appt at my dealership to check it out.

Well, a couple of nights ago, a coworker needed a jumpstart. Her Pathfinder was on the opposite side of a grass median, so I stuck my KJ in 4WD to climb up over it and get closer. When I was leaving, I failed to take the Jeep out of 4WD, so I got that terrible binding you get when you turn sharp on pavement in 4WD. I quickly figured out what was going on and put her back into 2WD.

Every since that incident, the shudder has been completely gone. No sign of it whatsoever.

Now, several weeks ago I made the same 4WD mistake, but turning the opposite direction. My theory is that I knocked something out of whack back then, and put things right by doing it again, but in the opposite direction.

Maybe someone who knows how this stuff works can explain what really happened.

In any case, all is good now.