Intermittent sound only while going down steep hills

[COminer]

I am struggling to trouble shoot a sound that has popped up a few weeks back that sounds a lot like rubbing on dust shield (metal rubbing on metal) but only while going down steep hills. The sound seems to track with wheel rotation (could be the drive shaft I guess) and varies while turning and going down hill but goes away completely when things level out.

I also don't have this problem on smaller hills in town only in the mountains on longer steeper hills. I have check the wheel wells and dont see anything loose and there is no sign of rubbing on the dust shields when i checked. I checked the heat shielding around the exhaust and that seems secure and shouldn't be able to touch the drive shaft.

Thoughts? Any help is appreciated.

 

[rightyouareken]

Possible wheel bearing starting to go perhaps?

 

[COminer]

Possible wheel bearing starting to go perhaps?

I thought wheel bearing too but find it odd that it goes away completely in town.

 

[rightyouareken]

I thought wheel bearing too but find it odd that it goes away completely in town.

So my theory was based on loading on the bearing when braking going down the steep hill. That would put more rearward force on the bearing than just tooling around town. Though you'd think that braking hard around town would cause similar loading and noise. What made me suggest this was your comment about it changing when turning, a classic wheel bearing symptom. Can you replicate it by swerving left to right at highway speeds?

 

[COminer]

So my theory was based on loading on the bearing when braking going down the steep hill. That would put more rearward force on the bearing than just tooling around town. Though you'd think that braking hard around town would cause similar loading and noise. What made me suggest this was your comment about it changing when turning, a classic wheel bearing symptom. Can you replicate it by swerving left to right at highway speeds?

Understood, loading is what made me think about the bearing too. It has not so far with normal highway driving but I haven't swerved much or had a lot of hard turns from speed or hard breaking that might give the same kind of loading. I will test that out.

 

[Hopeless Diamond]

Is it happening under engine compression braking, foot on the brakes, or under power? Manual or auto?

 

[COminer]

Is it happening under engine compression braking, foot on the brakes, or under power? Manual or auto?

Auto, foot on the brakes and under power. I can't say for sure if I have been using gearing to limit speed while it was happening or not.

 

[COminer]

I haven't been able to replicate the noise while swerving back and forth at highway speeds.

When the noise occurs when going down steep hills it is a fairly loud grinding/ rubbing sound, as I described kind of like rubbing on a dust shield. There was no noticeable noise when trying to get it to happen on the highway.

 

[rightyouareken]

I haven't been able to replicate the noise while swerving back and forth at highway speeds.

When the noise occurs when going down steep hills it is a fairly loud grinding/ rubbing sound, as I described kind of like rubbing on a dust shield. There was no noticeable noise when trying to get it to happen on the highway.

Have you tried popping the transmission into neutral when the noise is happening going down a steep hill? Also interesting might be putting the transfer case in neutral, but of course you should only do that when stopped and the transmission in neutral so it might be kinda hard to execute on a public road.

Depending on whether the noise changes or not when trying those things, it could point to whether this is a wheel/axle/driveshaft or engine/transmission related noise.

 

[AntleredRuin]

So only when going downhill?

Could it be a brake caliper? I lost a bolt in my passenger side a couple years ago, so it rested down on the wheel. It definitely made a good scraping sound.

 

[COminer]

Have you tried popping the transmission into neutral when the noise is happening going down a steep hill? Also interesting might be putting the transfer case in neutral, but of course you should only do that when stopped and the transmission in neutral so it might be kinda hard to execute on a public road.

Depending on whether the noise changes or not when trying those things, it could point to whether this is a wheel/axle/driveshaft or engine/transmission related noise.

Good idea, I will try that out.


And I don't know how I could have lot a bolt on a caliper but its worth checking at this point so I will double check that too.

Thanks for the input everyone.

 

[COminer]

Update:

The noise does not change when shifted into neutral when it is happening. It also doesn't seem to change when breaking, other than it seems to make noise based on rotation so it does change as I slow or accelerate.

The hill I'm able to test on it also takes going down hill for a while before it starts. The area it starts is maybe a little steeper and has tight corners and the noise is worse when turning to he left. This makes me think loading again but I tried to get it to make the noise by going faster, cornering harder up high on the hill and nothing. Nothing from breaking hard either.

I dont just want to replace the wheel bearing to see if that is it but I'm running out of ideas.

Any other thoughts?

 

[St Runner]

I am interested in what you find out. My 2001 tacoma does the same thing, makes a noise down steep inclines not related to braking, steering or clutch. Its hard for me to define the noise as it does not sound like metal and it is not that loud. In fact I never hear it that much because of the grinding loud metal that comes out of my stereo

 

[Izzeeeeh]

COminer, did you ever work out what the issue was? My car is doing exactly as you describe, the same sound and only downhill, and it stops as soon as it levels out. I’m desperate to know what the issue is!