Strange noises

[Chris K]

Thank you in advance for any help that can be given with my issue. My wife and I were out shopping one day in our 2006 Yukon and she was backing out of a parking spot and when she turned to back out she ran over something and it felt like it tweaked the chassis a little. No big deal these Yukon are pretty robust so I thought nothing of it. Later on that night driving home a rhythmic thumping and squeaking started under the vehicle. It was hard to pinpoint where it was coming from at the time. I have narrowed it down to under second row seat driver side in the fuel tank area. Had to fold the second row seat up to discover the exact location of the noise. The noise is very intermittent and has no rhyme or reason for why it starts except for that it increases in intensity with speed and hitting bumps will make it go away for some time but it always returns alternating between squeak squeak squeak and thump thump thump thump. The only way I can describe the sound is it's like an air chisel hitting a metal pipe like a machine gun rhythm then stopping and maybe squeaking a little bit and starting the hammering sound again. I've already greased the drive shaft splines, tried to inspect everything I could see, and hit connection points with a rubber mallet to no avail. I'm starting to get frustrated because I can't drive the vehicle with the racket going on. Any help is much appreciated.

 

[1999hoe]

Drive shaft maybe bad ujoint ? Dust shield on the back wheels it really could be anything but id start with looking at the ujoints and go from there

 

[swathdiver]

You gotta get under there and have a look around. Something got knocked loose or whatever she ran over is stuck underneath.

 

[Chris K]

I've already greased the drive shaft splines, tried to inspect everything I could under there, and hit connection points with a rubber mallet to no avail. I believe if the drive shaft U joints were bad it would make a consistent noise not stop and then start again 20 miles later. The sound is not at the back wheels it comes from the gas tank area. Under the second row seat on the driver side. Thank you for the ideas though.

 

[Doubeleive]

put it up on four jack stands, put it in gear and listen with a stethoscope

 

[UrbanSuburban]

As well as the above, check the exhaust as well, although it is in the fuel tank area, these noises can be transmitted through different parts. On top of the tank , the evap canister is near there, maybe it got moved and is not sitting correctly. As you say your wife ran over something, you should be able to see the area that was hit due to fresh markings. Good Luck

 

[dubyagee01]

I had a rear shock bend and finally break before I found that noise.

 

[Chris K]

The thing is with this noise that it's making is that it doesn't affect drivability in any way that I can tell. And I can barely feel it under my left foot on the driver side front floorboard. I would have someone drive me around and I would sit in the back to pinpoint it more with stethoscope but it's not making the noise right now and who knows when it will start again I could go another 100 miles and then it will start to make the noise again and continue for 50 miles and stop again. Does anyone know if ABS valves could make the noise I described in my first post and on an intermittent basis? That is the only mechanical thing in the area where the noise is coming from.