My 04 Wrangler with 4.0 auto has always done this but I wonder why. Only after some hot highway driving with cold a/c blasting do I notice this. When taking off from a stop the engine makes a noticeably louder roaring sound and seems to be working harder to accelerate. My wife even asks, "Why does it sound like that?". The temp is fine but at its highest point after sustained interstate speeds and stop and go St Louis traffic. The roaring eventually goes away and it doesn't always do it but I can't figure out exactly what's making the sound increase. Anybody know why? Any similar experiences? I hope I explained myself well.