I had some time on my hands and decided to try to fix the squeal. My blower came apart fairly easily. I supported the squirrel cage with 2x4's on end cut to about 6-8" and used a small metal shaft in my drill press to press the motor shaft down while holding the squirrel cage on the boards. Then I took out the two screws holding the motor in and pushed it out of the housing by the shaft. I can't remember how I did this, but it wasn't hard.
There are no bearings, only bronze bushings at each end of the shaft. Each one has a felt pad to hold oil. I used 3-in-1 oil, but it did stink for a while. I'm not sure what the proper oil should be.
My guess was the brushes were bad, so I removed the rotor. It turned out the brushes had about 50% of their length left. The commutator was fairly scratched up, so I put it on my wood lathe and filed the copper fairly smooth. You could do the same chucking it up in a drill press. I couldn't tell how thick the copper was, so I didn't take much off. I then used a small curved file to smooth the brushes while maintaining the correct profile. Both files were from a small file set from Harbor Freight.
The motor made a pretty bad noise for about the first hour after the rebuild as the brushes settled in. I've only used my 4Runner for about 1.5 hours since the rebuild, and now you can only hear a slight noise on the lowest setting. I assume that will go away, but it's still less than any road noise.
My guess is that just oiling the felt pads would have been sufficient, so I would have tried that first if I knew the brushes were still good. I recommend blowing out all of the carbon dust from the brushes. This dust is really messy.
