NP271 tcase issue
I have this 4x4 converted 2011 E250 van with a NP271 Tcase. During our last trip to baja I noticed that when going in reverse, the Tcase makes grinding noise and is jumping. Doesnt seem to be happening when on paved and flat ground, only on uneven ground when the van is on mud/sand and under load. More pronounced on 4x4 low. Are those symptoms of a streched chain? Does that Tcase need a rebuild? Can it be relates to imporper driveshaft angles/lenghts or worned ujoints? There was some recent work done on that van and they changed some angles with the driveshaft. Never really noticed before the work if that was an issue or not.
Video attached.
Thank you



