Service 4WD light appears noise when engaged in 4WD - 2006 5.3L 1500 Z71 has around 124,000 on it. When driving in 2WD, the Service 4WD light comes on sometimes. ...

2006 5.3L 1500 Z71 has around 124,000 on it. When driving in 2WD, the Service 4WD light comes on sometimes. After turning off the vehicle and restarting, the Service 4WD light will be off, but it has shifted itself into 4 Lo from 2 Hi. Just this week, we received enough snow that I used the 4WD for the first time since the light has been coming on. I notice a loud,winding sound from possibly the transfer case. When I accelerate, it feels like it is lose. I am wondering if it is completely getting into 4WD. There was a time that I was in 4 Lo and could not get it out. I turned the truck off, started it, pushed all of the buttons and did not have any luck with it changing out of 4 Lo. Finally after turning it off, it shifted into neutral and then I was able to get it into 2 Hi.

That sounds odd. First I would be sure your fluid levels are ok then re-evaluate things.

Also to engage 4 low your supposed to put the truck into neutral. But as far as the whining noise im not sure. Im not up to date with a lot of the newer transfer cases as far as the internals. But if they still have a chain drive in them, like a lot of older pick ups, then this may be some type of an issue. Or maybe even a bearing inside causing an overheating issue that is being picked up by a sensor in the transfer case causing your light to come on