First off this is on my '99 5.2 4wd. Have been experiencing issues with the transfer case...I think. Truck use to not have any issues shifting into 4hi from 2hi. Now it wants to really grind no matter how hard or fast I try shifting it (yes, I am driving at speeds anywhere from 25-40mph like you are suppose to). It doesn't have that smooth shift like it use to have. Also doesn't feel like it is always full engaging into 4hi. When this happens the truck will out of nowhere seem like the flywheel has is gone out (truck seems like its in neutral when in drive).

Where do I start looking???

 

Sounds like it is a linkage issue. Just look under the truck and see where the adjuster is and adjust it.

 

The np231 transfer case has a syncro in it for the "shift-on-a-fly" function. If it's not a linkage issue, I'm going to guess that the syncro is worn out. But start by checking the linkage, cause its more likely and much easier to check.

 

What is the correct way to adjust the linkage??