On my 1997 2500 5.9 auto. Going from 4 HIGH to 4 low in tcase got me gear grind. Any tricks to these cases and how to properly go to low range. I was not moving when I switched.

 

With the truck stopped, trans in neutral and the truck in 2wd. pull/push leveler into 4lo/or high. If in 4 hi just push it right into low.
With my truck if i leave the t case lever in neutral (on the way to another range) to long it will grind trying to get back into any range. I suspect the parasitic drag gets the gears turning, even in neutral. Then i have to turn the engine off and then shift to the desired range. However, if you just push or pull strait to the range you want it works every time! Just be sure your stopped and trannys in neutral. Works great for me.

 

Yep, things turn, even in neutral. If you find yourself with the t-case in neutral, just shut off the engine, wait a minute or two, then pull the shifter into the range you want.