I've got a 2000 Ford E250 5.4 2WD with 180K on her. I've had a strange noise ever since purchasing at 150K, but seems to have gotten worse/louder over last 6mo/15Kmi or so while taking her all around the west coast and across the country to FL. The noise kinda sounds like 2 flattened aluminum cans being rubbed together. Or maybe like chains being wound up on a spool. That's the best I can do to describe it. It only happens on acceleration, I'm thinking between 15-40mph. I don't really hear it on the highway going 50+ (I'm not sure if other road/engine noise might be drowning it out, but I don't think so). Noise stops as soon as I let off the pedal. I tried revving in neutral and I don't hear it. It sounds like it is coming from the front passenger side...if I am driving next to a wall or guardrail, I can really hear it.
This video was taken awhile back and it has gotten louder since, so I should probably have my lady film a better one (and with the windows closed), but if you listen close you can hear it at around the 5 sec mark.
Any ideas? Thanks for having a look (and listen!). -Parker