^ What he said. We need more info... The info we have to work with is contradicting itself when compared to the functions of the truck.
Like has been said before, you've got live axles and an open differential. Meaning the hubs are always engaged...the weak link out there is the CV shaft itself. It's a much stronger set up than the 98-99 PVH system. This also means all components rotate (driveshaft included) all the time, regardless of 2wd or 4x4(hi or low). Freespin is at the Tcase. The only disconnect/connect is the transfer case shift motor.
Now you shouldn't be switching in and out of 4hi with a heavy foot while rolling...that could lead to that small pinion taking a good hit or transfer case complications.
How are you determining a CV shaft is "disengaging"??
'01 XLT disguised as a '03 Fx4 Level II
Big. Loud. Slow. Bright.