Whistling sound comming from under hood

[niowa98eb]

First off Merry Christmas to everyone.

the wife and I took a trip to Indiana yesterday and about 6 hours into our trip we noticed a whistling sound coming from under the hood of the Expy. I pulled over to check some thing out and couldn't find anything and it wouldn't make the sound while we were in park. Could this be a vacuum line that's cracked or dry rotted? I thought it could be my transmission but I put the truck in N when it was making the sound and it still makes it for a few seconds then quits.

 

[niowa98eb]

forgot to say it happens most frequently when the rpms are around 2k just before it shifts into over drive and not if I floor it from a stop light.

 

[2000eb]

sounds like my tb spacer... did someone prior to you add a tb spacer?

 

[Thermo]

I was thinking throttle body spacer too.

 

[niowa98eb]

Not sure if someone added a Tb spacer before me but this just started after owning my Expy for a year now. I'm going to pick up some mercon today and add some to see if that takes care of it. if not I guess I'll be taking it in to get checked out since were about 700 miles from home. Thanks for the help.

 

[SkyJumper]

Have you added an aftermarket air intake cone filter in place of the stock air box? Those torpedo chrome cone filters from the auto parts stores make a whistling sound when the gas pedal is applied. It is created from the inner chrome torpedo head inside the tunnel of the filter.

 

[niowa98eb]

Added some mercon and the sound is gone must have just been low. No aftermarket intake or tb spacer. Hopefully it was just a little low on tranny fluid thanks again guys for the suggestions.

 

[2000eb]

never heard a tranny a little low on fluid make a noise like that... thermo? whats your o2

 

[niowa98eb]

$178, 3 vacuum lines, 2 elbows and a new pcv valve and the sound is gone. Hopefully it stays gone.