Here is a strange one that I hope someone can help with..Just purchased a 2001 Super Crew. Noticed a very high frequency sounding noise coming from the speedo cluster area while driving, it comes and goes. Has anybody ever heard of this? I hope you can help..Thanks It is 4X4 with a 5.4

 

Probably in the wrong area here, check under the engine forum, you'll find a lot of information from there on where to start checking. This is a common problem, ranging from the IAC to vacuum lines, to even holes in the firewall.

 

Thanks, I'll check there. Although I believe it's and electrical noise, does it with the radio off as well.

 

Do you have a 5.4? If it sounds like it is coming from the dash than it sill could be the IAC, as it is mounted real close to the firewall and right about where the defroster vents are on your dash. Most trucks seem to have the problem at certain RPM's. I don't think there is anything in the speedo area that could cause the whine, the noise is coming from the engine bay, just need to rule out the most likely culprits first.