Whirling noise coming from under truck. Need advice.
March 4th, 2013, 7:33 PM
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Whirling noise coming from under truck. Need advice.
First off, I'm a newbe to the forum and sad to say while I know enough to keep a car up, (change my own oil, brakes, etc..)I'm pretty truck dumb when it comes to 4X4's and SUV's so please don't judge me too harshly off my questions. 
I'll start by giving some information about my truck. 03 Chevy Tahoe. All the original parts are in the vehicle and anything thats been replaced was replaced with OEM parts or something comparable. I drive the truck approx 46 mile round trip to work each day from Suburban Maryland to Wash DC so it's not like I'm in the Mountains or constant harsh temperatures. It's never been used for off roading and I've only towed something once, a half empty UHAUL trailer. I've only used the 4 wheel drive once since I've owned it a few years ago to pull a stuck friend out of a snow bank. Other than that, the truck has the 4WD auto and the 2WD button. I keep the truck in 2WD since I have no need for 4WD.
Now on to the issue. My 03 Tahoe Z71 has a whirling sound coming from under the truck. Not loud enough to be noticable but loud enough for me to know it's not normal considering I drive the truck everyday. It sounds a little louder near the rear but I can't get a pinpoint on exactly where it's coming from. The sound starts soon as I crank it and stays constant no matter if the truck is moving or standing still. It doesn't get louder or go away after the trucks warmed up. Just stays the same. After doing some research I thought maybe it could be the differential so I took it to have the oil levels looked at. The front was clean and clear but the rear was almost empty. I was told that oil dissipates and being almost empty could be possibly due to me not having it looked at since I've had the truck (approx four years now). I had rear and front drained and filled back up and the gasket replaced on the rear. Took it back to the same shop a week later for a followup and the shop said that both showed no signs of leak and had clean oil (I took it back for a followup because I've read that if you hear any sound then likely you'll see dirty oil or metalic shavings in the oil). So by all current knowledge nothings wrong with differential BUT the whirling sound is still there. So now I'm scratching my head. Thinking about taking it to a dealership and having them look at it but after prior experiences I have zero confidence in the Chevrolet dealership close to me. I'm almost certain they would "fix" thirty expensive things that aren't broken before telling me what really is (long story). Which means I'd have to take it aways out to have it looked at else where. Before going that route I'm hoping someone else may have had this issue who may be able to offer some help. Thank you in advance for any input.
I'll start by giving some information about my truck. 03 Chevy Tahoe. All the original parts are in the vehicle and anything thats been replaced was replaced with OEM parts or something comparable. I drive the truck approx 46 mile round trip to work each day from Suburban Maryland to Wash DC so it's not like I'm in the Mountains or constant harsh temperatures. It's never been used for off roading and I've only towed something once, a half empty UHAUL trailer. I've only used the 4 wheel drive once since I've owned it a few years ago to pull a stuck friend out of a snow bank. Other than that, the truck has the 4WD auto and the 2WD button. I keep the truck in 2WD since I have no need for 4WD.
Now on to the issue. My 03 Tahoe Z71 has a whirling sound coming from under the truck. Not loud enough to be noticable but loud enough for me to know it's not normal considering I drive the truck everyday. It sounds a little louder near the rear but I can't get a pinpoint on exactly where it's coming from. The sound starts soon as I crank it and stays constant no matter if the truck is moving or standing still. It doesn't get louder or go away after the trucks warmed up. Just stays the same. After doing some research I thought maybe it could be the differential so I took it to have the oil levels looked at. The front was clean and clear but the rear was almost empty. I was told that oil dissipates and being almost empty could be possibly due to me not having it looked at since I've had the truck (approx four years now). I had rear and front drained and filled back up and the gasket replaced on the rear. Took it back to the same shop a week later for a followup and the shop said that both showed no signs of leak and had clean oil (I took it back for a followup because I've read that if you hear any sound then likely you'll see dirty oil or metalic shavings in the oil). So by all current knowledge nothings wrong with differential BUT the whirling sound is still there. So now I'm scratching my head. Thinking about taking it to a dealership and having them look at it but after prior experiences I have zero confidence in the Chevrolet dealership close to me. I'm almost certain they would "fix" thirty expensive things that aren't broken before telling me what really is (long story). Which means I'd have to take it aways out to have it looked at else where. Before going that route I'm hoping someone else may have had this issue who may be able to offer some help. Thank you in advance for any input.
March 4th, 2013, 7:55 PM
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If the sounds is the same when its not moving, then its definitely NOT a rear end or front end. I bet the fuel pump is making the noise. See if you can isolate it to the gas tank in the rear.
March 4th, 2013, 11:53 PM
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I agree. The fuel pump sound should be noticeable when you first turn the key on but then should go silent as the pressure limit is reached.
Do you hear w/ the key on, engine off?
Do you hear w/ the key on, engine off?
March 5th, 2013, 7:03 AM
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Agreed. I'd fire it up or have someone cycle the key while you listen around the gas tank...
The 01 I had whined constantly, never failed, but whined non-stop.
The 01 I had whined constantly, never failed, but whined non-stop.
March 5th, 2013, 11:00 AM
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My '97 Z71 pickup and my wife's '02 Tahoe both lost fuel pumps within a year of each other. The 97 always made a "whirring" sound as described previously, while the Tahoe was silent.
March 10th, 2013, 7:57 PM
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thanks for the answers
Haven't had a chance to sign in here in a few days but thanks in advance for the responses. No I haven't thought to isolate the feul pump and to be honest, thats the last thing I thought of. I guess with my truck getting so high in miles I've been a little over paranoid with something big breaking that I tend to forget the little things. 
I don't have the service record but if memory serves me right the feul pump was replaced three or four years ago. Some kids in my neighborhood were being jackass's and thought it would be a hoot to put sugar in a few of the tenants gas tanks (luckily I noticed it before cranking my truck up). The insurance co. thought it would be a good idea to replace the feul pump just incase. So, long story short the feul pumps less than four years old. I've got a dayoff this week and I plan to put it up on some ramps to have a listen.
So my next question is, given the feul pump is less than four years old if it is the culprit should I still consider having it replaced? I saw that hicksvilleshick said theirs made the sound also but never failed.
I don't have the service record but if memory serves me right the feul pump was replaced three or four years ago. Some kids in my neighborhood were being jackass's and thought it would be a hoot to put sugar in a few of the tenants gas tanks (luckily I noticed it before cranking my truck up). The insurance co. thought it would be a good idea to replace the feul pump just incase. So, long story short the feul pumps less than four years old. I've got a dayoff this week and I plan to put it up on some ramps to have a listen.
So my next question is, given the feul pump is less than four years old if it is the culprit should I still consider having it replaced? I saw that hicksvilleshick said theirs made the sound also but never failed.
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March 10th, 2013, 8:03 PM
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I've only noticed it when I crank it up but I didn't even think to just turn the truck on/engine off and see if I hear the same noise. I'll check in to that when I get home tonight.
March 10th, 2013, 9:50 PM
#9
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Put your ear to the fuel filler, does it sound like it is coming from inside the tank? I have seen many times on GM trucks where the fuel filter becomes very restricted thus causing the fuel pump to work to hard which makes it louder. Sometimes if caught soon enough filter replacement will quite down the pump. If not caught soon enough pump failure will eventually happen.
On a side note sugar will not dissolve in gas. All that needs to happen is removal from the tank. Because the pump has a "sock" on the bottom the sugar can never get into the pump or injectors.
On a side note sugar will not dissolve in gas. All that needs to happen is removal from the tank. Because the pump has a "sock" on the bottom the sugar can never get into the pump or injectors.