I had a company owned F250 with a 6.4 from new to about 160,000 miles. It had troubles too. I drove it in for repair a few times and it was towed in once as well. Around 110.000 miles it seemed to run pretty well and behaved pretty good. Other 6.4s in the fleet had various troubles too. A buddy that farms had a 6.4 too and it was having trouble. He sent a engine oil sample in for analysis like for his tractors and combines and it came back as "stop driving immediately" because of metallic deposits. Showed the results dealer and they said drive it because of warranty and they would handle it as troubles came up. He eventually traded it for a 6.7 and he likes that one.