I have a 2004 F150 FX4 with about 15K miles. Over the past few weeks every now and then the transmission makes a very loud grinding sound (from the front) when driving. There is nothing that triggers it sometimes it happens when going slow, sometimes when going fast. The only way to stop the sound is to come to a complete stop. As the transmission gears down it does so with a clunk until the truck is stopped. Then when you accelerate it is fine, and may not make the sound for another few days. I had the truck into the dealer and they drove it and couldn’t get it to make the same sound. They replaced some parts in the rear diff. as they said there was gear noise, but nothing for the loud grinding sound they couldn’t replicate. I’m just wondering if anyone else has had a similar issue?