Squeeling noise while coasting 02 sierra 1500

[Accelerator]

I have an 02 gmc sierra 1500 5.3 liter V8 with 206,000 miles on it (still going strong). There is an odd squeeling noise that occurs whenever I coast at low speeds (below 40 is when it usually starts). It goes away as soon as I give it gas, it does not occur at all while the vehicle is stopped. I am decently mechanically inclined and yet I cannot figure out what would cause it to happen only while I was coasting. I've had others listen to it and no one seems to be able to figure out where it is coming from. Thank you for your help.

[txab]

I'd check the driveline for starters. U-joints, carrier bearing etc...

[Jsdirt]

^^^ +1 ... what he said.

[Doug_Scott]

First couple of things I would try that don't require me to lay on the ground are first, putting the truck into neutral while noise is going on. Does noise change? And again, while truck is moving and making the noise, manually shift the truck into a lower gear, does noise change? While truck is making noise, shift into neutral, any change? And the trickiest one for last, make sure no one is around, road is straight, and weather is good. Get the truck making the noise, now turn ignition key back ONE spot. This should turn engine off, without locking steering wheel. If none of those 3 made any appreciable change, then the noise is after the transmission.

 

When you say it will not do it with truck parked, do you know if it does it with the back wheels off the ground?

 

You didn't say if truck was 2 or 4 wheel drive.

[Accelerator]

Thanks for the response guys! The truck is 4wd, I live in the sticks of West by god Virginia so having a truck without 4wd wouldn't do me any good.

 

I've tried all of those suggestions except for jacking up the rear wheels. No change in the noise. A little more information: The noise is intermittent. It really only does starts after I've been driving for a while. I'll try jacking up the rear tires tomorrow.

[gmtech4]

im not convinced that raising the tires will reproduce the concern because of the lack load on powertrain during a coast situation ,,,

 

let us know

 

check diff oil levels and condition for giggles

 

and what txab said ,ujoints load up driveline angles and create a squeak rotationally,,,block wheels and remove shafts and rotate them ,a seizing ujoint will jump out at ya ,,,no need to mark shaft location except the middle slip yoke on 2 pc shafts

[Doug_Scott]

im not convinced that raising the tires will reproduce the concern because of the lack load on powertrain during a coast situation ,,,

 

Only suggested it because it was easy, free, and if noise appears, makes it easier to walk around to locate the source.

 

 

 

and what txab said ,ujoints load up driveline angles and create a squeak rotationally,,,block wheels and remove shafts and rotate them ,a seizing ujoint will jump out at ya ,,,no need to mark shaft location except the middle slip yoke on 2 pc shafts

 

If you have the grease pencil out to mark the middle slip yoke on 2 piece shafts, then it will not add any time to the job to mark all shaft positions. It can't possibly hurt to do this. As I have posted before, I have had numerous experiences where putting a single drive shaft back in place 180 degrees from the original position created a pulsing low frequency drone type vibration at 35 to 45 mph. Unbolting the shaft at the rear u-joint, and turning shaft 180 degrees (half rotation) instantly stopped the vibration. I have no idea why it would do this, since no factory manual at the time said to mark shafts. Manuals did however say to mark pinion flange to pinion gear position when changing pinion seal. I never did a pinion seal without marking it, so have no hands on experience regarding what happens if orientation is not kept.

 

Your post reminded me of an issue I had once with a fairly new 400-4bbl Power Wagon. It had a strange squeaking noise at about 40mph. Noise sounded like it came from dash, on the right side near windshield. Spent hours trying to locate the source. Went out on a road test with one of the older mechanics(he was near retirement, and was teaching me auto trans rebuilds), he said to pull drive shafts out because he could feel a vibration in the dash. Turns out one u-joint had a cup that was very tight and hard to get off, and once off you could see the grooves worn in the u-joint surface. Replaced that u-joint, put shafts back in(all were marked) and went for road test, Noise was gone, and the vibration that I never did feel was also gone according to the other mechanic. Never did find what in the dash was squeaking.

[Netgunner]

I am having a similar issue. 2004 Chevy Avalanche 1500 4x4 Z71. When i am driving..about 5 miles down the road and above 15 MPH i begin to hear a whining or very faint grinding noise coming from under the vehicle. Once i get her up to 50 or better the noise goes away. I took it to the dealer and without taking anything off they told me that i would require Ring and Pinion and Bearings. Total cost $2375.00. Thye also mentioned front axel seals require replacing.

I do not have the funds to pay the dealer but have a fairly decently equipped garage. Thinking of performing the repair myself. Dont want to replace what isnt broken...any suggestions?

 

Have a 2000 miles road trip coming up in 5 days and only have the rest of today and sunday to work on this. Any help is much appreciated.

[02suburbanZ71]

I am having a similar issue. 2004 Chevy Avalanche 1500 4x4 Z71. When i am driving..about 5 miles down the road and above 15 MPH i begin to hear a whining or very faint grinding noise coming from under the vehicle. Once i get her up to 50 or better the noise goes away. I took it to the dealer and without taking anything off they told me that i would require Ring and Pinion and Bearings. Total cost $2375.00. Thye also mentioned front axel seals require replacing.

 

I do not have the funds to pay the dealer but have a fairly decently equipped garage. Thinking of performing the repair myself. Dont want to replace what isnt broken...any suggestions?

 

Have a 2000 miles road trip coming up in 5 days and only have the rest of today and sunday to work on this. Any help is much appreciated.

 

Take it to a few local transmission shops for an estimate.

[gmtech4]

unless you have done this repair before you should really rethink this ,,,,

 

It needs an above average skill level for this repair , tread carefully , I'm tellin ya bud , don't do it