97 Explorer Making loud Revving noise while slowing down

[jranderson8181]

Hello,

First post on the forum for me

I have a 97 Explorer 4x4 with V6 SOHC with 164K

Yesterday while driving it started making a loud revving/Vacuum sound (kinda hard to explain) only when I am coasting/slowing down. As soon as I accelerate, the noise stops.

It only happens when I am traveling at higher speeds around 55/60 mph and when let off of the gas to slow down the noise starts right about as it gets below 2000 rpms and continues until you bring it to a stop or resume acceleration.

It does not make this noise at idle and I can not duplicate it while revving it up in the driveway. It only happens when the vehicle is in motion. I can not tell a difference in the way that the vehicle is operating, other than hearing this noise. My neighbor mentioned that it could be the fan clutch, but it was too dark to check it out last night. Has anyone else had a similar issue, or any ideas?

Thanks!
Jeremy

 

[Kevlar7R]

My first thought was fan clutch, but it would make the noise pretty much all the time.

A vacuum leak wouldn't make that much noise.

When it's making this noise, watch the tachometer and see if the engine is actually revving up. If so, it could be an idle air control issue.

 

[jranderson8181]

Hello,

Thank you for the reply. Yeah, I figured a bad fan clutch would have a constant noise as well. When the noise is occuring the RPMs are actually dropping which has me stumped.

 

[drdoom]

Sounds like transfer case needs a rebuild.

 

[MJK17]

Jeremy,

I realize this was a couple years ago, but did you ever figure out the problem? I'm experiencing the exact same thing, and have found several postings about it, but none of them have a conclusion... Any help would be appreciated!

Thanks,
Matt