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Service 4WD

2005 Chevy Avalanche Z71.

When using the 2 wheel drive mode I get a Service 4WD indication in the odometer screen. The drive selector at this point becomes inoperable; if left alone it will sometimes shift into 4WD Low range during or shortly after engine start. I can then turn power off and it will usually reset and I can put it back into the Auto 4WD mode. If left here there is usually no problem other than what seems to be an unnecessary engaging of 4WD when braking during a turn. The result is a sort of grind and jolt as the stop is completed. I have replaced the selector switch which seemed to help as I was able to operate in 2WD mode for about 3 days. Just as I started to trust it was fixed the service 4WD indicator came back and continues whenever in the 2WD mode. I have been told now to change the 4WD actuator which is a more expensive part. It seems that someone should know what the true solution is rather than just hit or miss part changing. The dealer?s service department doesn?t seem to have a clue.

Thanks for any suggestions,