FYI, the grinding you are hearing is from the transmission input shaft free-turning which "cause and effect", as you shift into 4L, you pass thru neutral on the t/case which allows the output shaft of the transmission to free-turn as there is no resistance on it, this allows the t/case input shaft to turn-freely. The gears are not lined up as it was in 2H/4H and you hear the grinding of the t/case gears.
You can shift into 4L with the transmission in park, but you may need to jerk it into gear as the free movement of the gears is now stopped.
Neutral is the lesser of 2 evils.
In newer vehicles with the push button 4WD, you get a clunk when it engages 4L as the gears align themselves.