I've recently purchased my very own 1989 Grand Wagoneer! Now that its running quite well it was time for me to dig into the convenience features on the interior. I started working on the rear windows and door locks.
This is my experience and it may make life easier for someone in the future.
Both rear windows would not budge! I could hear the motor click, but no motion at all. So with the door panel removed, i began dis-assembling the guts of the door. First was to remove the window regulator. My 89 does not have the flex track style regulators, but the metal coils with red felt in the middle. After working to get the screws out that hold the window to the regulator, i was able to test the motor. To my surprise, the motors worked just fine! Full range of motion with nice speed. Dodged a bullet there as those motors are difficult to source. Once the regulator was out, i cleaned out the tracks and gave it a nice layer of sil-glide. Set that aside and moved on to the glass that i left in the UP position.
Since the glass was just floating up there, i determined that the rubber & felt tracks were the culprit. Attempting to move the glass by hand was possible, but clearly was being held up by the dry inflexible tracks. There was also audible cracking in the rubber as the glass moved. I was able to disassemble the window to the point that the vent window, and the rear divider bar was loose enough to remove the glass. I then removed the window wipes and the divider bar. At this point all the window components were out of the vehicle. Take your time. Things are tight, and there are screws on the door frame that hold in the little rectangular vent windows. Without those out, the divider bar will not move. On to the locks.
With much more room to maneuver since all the window stuff was out, i could clearly see all the power lock linkages. My power lock actuators moved, but not well enough to actually push or pull the lock bar up or down. it just jiggled. So i started with some silicone spray lube on all pivot points in the system. I worked it in by manually locking and unlocking the door. Things got easier. I tried the power lock button and it was still not working. It was better, but not fully locking and unlocking. I discovered that on the latch side of the door where the lock linkages finally move the lock at that latch, that it was caked with old white-lithium grease from a previous owner. Grabbed a can of brake cleaner and manually worked the lock while spraying. The old grease cleaned right up and with that, the power lock was working like a champ. The old grease must have placed enough resistance on the system to stop it from working. Once it was working well, i applied sil-glide to all pivot points. LOCKS DONE! Lucky me, it just needed cleaned and lubed.
After waiting for my new replacement tracks and rubbers for the windows, i was able to reassemble the windows. I now have 2 rear doors that have fully functional windows and locks! Now on to the front.
This just took time, lube and some basic tools. The first door took almost 3 times as long as the second. Experience counts for a lot.
Hopefully you find this useful and it helps to motivate you to get your FSJ back to tip top shape!
John