I have retro-fitted electric locking differentials in to my 88 SAS truck. I am having a problem with the electric motor assembly in the rear not working properly. I have taken the motor apart many times trying to get it to work.

The electric motor has a worm gear that drives a round plastic gear with a metal tab that engages the spring. I think that the problem is that the metal tab is hitting the raised mechanical stop enough to get stuck on it. The mechanicial stop is a raised area of the aluminum cover. The corner of the mechanical stop is worn down, so that the metal tab will get stuck on it causing it to jam the motor. It seems to me that the limit switches should stop the motor prior to it hitting the mechanical stops.

I am using carterman's schematic and testing it with the limit switches connected per the instrucions. I also have a high pinion in the front and it works fine.

One other thing. The motor is kind of noisy compared to the front one. Also, it looks like the motor may have had some moisture in it at some point. There appears to be a little white corrosion present. Has anyone else seen this in the motor assembly?

Any ideas on how to make this work properly, or do I need to see if I can find another one?

The little but of corrosion should not be a problem.
When I took apart my motor, there was corrosion and sand in it. I was able to clean it out and I greased it up really well, and the motor worked great.

How is the motor "not working" is it not turning, not turning enough? stalling out?

I can get it to run, but the metal tab will jam against the raised mechanical stop on the cover plate. I am using the limit switches, but it seems to go too far, then it gets stuck.

Hmmmmm. The limit switches are on the worm gear attached to the worm. Is it possible the worm gear is out of rotation?
I assume when you run into the mechanical stop, the motor is still trying to turn.

If you look at the worm gear there is a weird shaped metal cover on one side that comes into contact with three copper contacts. When the gear is rotated enough, one of the copper contacts runs out of metal on the gear, stopping power to the motor (limit switch). I can't remember if the worm gear is notched to prevent a bad gear orientation or not . . .