Rob:

This is the only thing I know of that you didn't already mention, so take it for what it's worth (which ain't much <img border="0" title="" alt="[Wink]" src="images/icons/wink.gif" /> )

I had an '89 Cruiser with the same symtoms you describe (fluid was full and not obviously roasted, goofy shifting, etc.). Sterling McCall Toyota in Houston (I knew the Service Advisor so I doubt it was a hose-job) found the problem to be a snapped "detent cable". Now I couldn't even guess whether the Jeep tranny has one, but the cable runs from the throttle to the whatchamagizmo-thingy inside the tranny that actually controls shifting. Apparently, this cable (along with the vacuum inputs) tell the tranny to shift or not. Both vacuum and the cable were required to function normally, but either one would provide a "limp-home" mode should the other be damaged (like mine was).

Again, I know squat about Jeep slush-boxes, so your mileage may vary, other terms and conditions may apply, not valid without coupon, see store for details.

Good luck, (hope this helps)
Kevin V