I have a 1999 Dodge Ram 1500 V8 5.9. When I am pulling anything or going up hill or accelerate quickly it has a loud rattle that is almost null and void when on a flat road going the same speed. But once I put it under any strain it gets louder. It is significantly worse when I pulled a 22ft camper a few miles. Did not like that at all. I have done seem reading and am wondering if it is more likelly the valve lifter or the pelnum gasket? Or am I way off? The rattling is coming from the front.