4 High grinds but 4 low works fine?

In 4 high transfer chatters but 4 low no problems. Runs fine otherwise?

 

Even on a 'slippery' surface? If so, try changing your transfer case fluid.

 

Any time in 4 high, feels like gear(s) slipping or an axle clicking. But doesn’t do it in 4 low or 2wd

 

Doesn't sound like it is going fully into 4 hi position.

 

Any suggestions?

 

That sounds pretty strange.
The high/low range gear is a planetary gear set up at the front of the transfer case.
The 2/4 gear is locking or unlocking a sprocket from the main shaft near the back of the transfer case.

The fact that it works normal in 2H suggests that the noise is not from the high/low range gear.
The fact that it works normal in 4L suggests that the noise is not from the 2/4 gear.

The only thing I can imagine it being, is a misalignment in the shift linkage. If it moves the linkage a little bit too far towards low when in 4H, then it might be skipping at the edge of disconnecting the main shaft, i.e., its almost putting it in neutral between 4H and 4L.