I tried getting into 4lo once at about 5 mph and the thing made a horrible grinding noise so I immediately gave up on that and have never tried again. I have went into 4hi a couple of times at around 30mph with no issue, but I still usually stop and but the truck in park or neutral before swapping into 4hi or lo.
Apply dirt liberally, rinse and repeat
<<<-click for build
cut a bit
Lifted it more
welded a lot
cut some more
Got a winch
Parked until I can get a new steering setup.