Most Indy mechanics and even dealers don't reset the transfer case oil wear...because vehicle is our of warranty anyway
To test the t-case, you'll need at least 3 wheel rollers or heavy snow+ice. The idea is to make the vehicle deliberately lose traction and have the 4x4 light activate. Then you'll want to use INPA or ISTA to see if there is a transfer case malfunction code....if there is, you'll need a new one of you have stuttering/noise issues, etc.
To turn on t-case/off: