I have put two sets of gears in my 5.0 now and have had the same problem with both of them. The bolts on the ring gear back themselves out and sit in the oil until some perfect powershift and grind their way into the gear set. Now the first set I put in myself and used high strength locktite and the second time I took the axle to a shop and they did it all. It lasts about 6-9 months of driving until disaster strikes. Any ideas?