When I engage the 4x4 selector **** to 4hi when truck is moving all I get is a grinding sound. Seems to be coming from the transfer case. As I slowley come to a stop it clunks and engages it 4x4 hi. When I shift back to 2 wheel drive there is no problem when moving or stoped. Has anyone had a similar problem? The truck has 111K and has been well taken care of along with regular fluid changes. Thanks for any info.

 

While it may not necessarily address your problem, have you ever changed the transfer case fluid?

 

There is a small motor that engages the transfer case into 4x4. As time goes on, they can get dirty and/or worn. It is mounted on the top of the case, (If I remember right), and is not to hard to remove for cleaning or replacement. If it starts to get dirty or worn, it does not have as much "Umph" to kick it into 4x4.