2001 Silverado - Strang "moaning" noise when driving past 50mph
 

Heya fellas. I am hearing a kind of weak moan coming from under my hood. It only happens past 40-50mph while on the freeway. If I shift to neutral while at 60, I never hear this noise at all... not until I shift back into Drive. Once in drive, the noise returns within 20 seconds.

I am no expert... but it sounds like a humming moan of minimal friction between metal parts that do not have enough oil to lube them.

I just took the truck in for an oil change. They said it was 1/2 quart low... I don't think that's too big of a deal to worry about.

Within 1 mile of getting on the freeway, it comes back. Its kind of faint... and only happens for about 2 or 3 seconds at a time... and maybe 2 or 3 times per minute. Like I said.... coasting at 60mph and the noise immediately goes away.

Specs:
2001 Chevy Silverado 2X4 Ext. Cab
Automatic 5.3 V8
Bigger than normal wheels/tires
72,000 miles

Thanks!

Get that dog from under your hood and stop driving over poor defenseless animals !!!

This could be pretty much everything, really. Your brakes can be sticking to your brake disc.
It could be the (metal balls inside your axes that allow your wheels to turn) "lagers" ? (but thats beer right?)
Since it doesnt happen when shifting to neutral, i think its a transmission problem. Did they check the fuel of your transmission as well? Is there enough in there (not too much though...), what colour is it? Is there ashes in the bottom pan or on the filter? ...

Does the 2001 have electric cooling fans, maybe a bad fan motor cycling off and on and only with a 50 mph wind in it's face.

Transmission Fluid makes sense.

I replaced the Fuel Filter Recently, along with hub bearings, new rotors, and new brake pads. I don't think any of these new changes are a part of the problem.

I will check the transmission fluids and update.

One place told me my trans. fluid needed to be replaced, but then AAMCO told me it was just fine. The first place was known for trying to add things to the bill.