2004 silverado 2500HD crew cab 6.0L 4X4 auto trans, manual shift transfer case.

found my transfer case lost all its fluid & tore some stuff up. I took it to a reputable transmission shop for a rebuild. After putting it back together there was a growling sound that he wasn't satisfied with. He took it apart again & inspected everything & couldn't find the problem.

It's now back together and I'm driving it, 4WD is working, but here's the symptoms:

slight ticking/grinding sound in 2H, gets louder in 4H (seems to be resonating up through the floor shifter)

Now, the N & 4L positions on the transfer case is where things get hairy. While the truck is idling in neutral, trying to shift the transfer case into N is about impossible, it grinds like crazy. Turn the ignition off & the grinding will stop & allow you to shift between N & 4L but it does take some finagling. It seems that none of the transfer case shifting, although working, is nearly as smooth as it used to be.

Please help