Service 4WD/Encoder Motor

[dpattee]

Hey guys, I know this is a topic that has been talked about frequently, but I am looking for some advice. I have a 2005 Tahoe LT with about 165,000 miles on it. Two years ago, my Service 4WD light came on and the Traction Control was turned off. After much research online (dealerships are no help) I discovered the Encoder motor sensor problem. Replaced the sensor and 4WD worked great, for a few months. Same situation again and fought with it for a while. Replaced the switch, and no help. So, replaced the sensor again. But this time there was lots of oil inside the motor when I took it apart. What could that be from? Replaced the sensor, and everything was fine. Now I am getting Service 4WD on the dash, the 4WD switch is lit up, but I cannot switch between 2WD and 4WD. This only happen intermittently. It seems to be worse after it rains, or is wet out. (Morning dew) Just trying to figure out next steps. Should I bite the bullet and replace motor? why would there be oil inside the motor? Seal seemed tight when we replaced sensor and bolted the motor back to the drivetrain. Looking for some assistance here guys. Thanks.