While pulling my small fishing boat from the river the 4wd actuator broke. With the boat on the front hitch the rear tires spun. (no jerking just spinning). Made it back to unload the boat. Continued to check the 4wd thought I heard the actuator engage checked to see if the front tires would throw up grass on level ground in high gear when the rear differential came out of the frame. Found the cross member with faulty welds on both ends and tabs where the cross bolt on the diff attaches ripped from the cross member. While trying to drive carefully to near by metal shop the machine kept dying. After removing the muffler to gain access for welding up the frame, found the muffler completely stopped up. Made welds, left muffler off and ran like it was supposed back to barn. 2011 HDX with 1123 miles kept in barn never left out doors primary paved roads to visit neighbors and launch small fishing boat.