Chalk one up for my daughter. We started getting an intermittent grinding noise while driving our Jeep. It is pretty hard to figure out the source of noise like that, but it seemed to be coming from the transfer case area and varied with vehicle speed. I did a lot of fiddling, trying to isolate the source over the course of several days. When I had deduced, with no small amount of reason, that the output shaft bearings had failed in the transfer case, she asked if I was going to fix the speedometer, too. Only then did I look down to see the needle gyrate in synch with the noise.

Lubing the speedometer sure beats pulling the transfer case. Remove two wing nuts and the drive cable to pop out the speedometer. Disconnect the battery as unfused power is present at all times on the terminals of the adjacent ammeter.

From the WillysTech Mailing List, I learned that on the back of most speedometers there is a small oil hole. The hole is partially blocked by an adjacent screw head. There is no need to remove the screw to add a few drops of oil. Spin the input shaft by hand a few time to distribute the oil:

If your speedometer doesn't have this oil hole, you can still add a few drops of oil where the cable enters the back.

While you have the speedometer removed, pull out the core of the speedometer cable from the top. There is no need to unscrew the other end of the cable. Wipe the cable core clean and lightly lube that, too. As you feed the core back in, spin it gently by hand and you make sure you feel the far end mesh with the drive gear inside the transfer case.