Low Hum Sound

Aloha guys! Haven't posted in this section in a while. I've got an 06 DC Sport, AT and have been recently experiencing/noticing a low humming sound when moving. It seems to be dependent on the truck's speed i.e. as the truck's speed increases the humming get's louder and vice versa. It seems to be loudest at around 45 to 50 mph. At a stop, there is no sound. The sound is only audible inside the cabin. I had the truck do some passes to see if I could ear it outside, but I could hear nothing.



I thought it was the tires at first, but my tire tread (stock sport) is almost gone and I never had this before. I don't think it's the engine since the sound doesn't go away when placed in neutral, when moving. I shifted through all 5 auto gears and all seem normal. No other weird sounds. Just concerned here that something's wrong.



Any ideas on this are greatly apreciated. My bumper to bumper warranty is gone, but the powertrain is still intact. I haven't had the best of experiences with my local Toyota dealership here, but will go to them if nothing else.

Reply 1 : Low Hum Sound

Quote:

Originally Posted by musubi I thought it was the tires at first, but my tire tread (stock sport) is almost gone and I never had this before.

Tires get noisier as they wear out... the culprit may actually be your worn tires. Even though it may not be noticeable from outside the truck, there may be some odd harmonics being introduced into the body structure, making it audible from inside.

Reply 2 : Low Hum Sound

How often do you rotate your tires? A common cause of the type of noise you're describing comes from "cupping" when tires aren't rotated frequently enough.

Reply 3 : Low Hum Sound

Rotating them might help. Those cheap Dunlops are probably at the end of their useful life anyway. Cupping of the tires could indicate bad shocks too. Take a look to see if the look like this: Tire wear

Reply 4 : Low Hum Sound

Thank you all for your thoughts on this. I've been trying to think of how to isolate this noise. I was thinking driving over grass would prove or disprove the tires, but I can't find a flat stretch of grass. I'll see if rotating the tires solves the sound. And no, the tires are not oddly worn in any way. I almost want to place the rear on stands, run it and see if the noise occurs, but that sounds like an accident waiting to happen.

Reply 5 : Low Hum Sound

Quote:

Originally Posted by musubi Thank you all for your thoughts on this. I've been trying to think of how to isolate this noise. I was thinking driving over grass would prove or disprove the tires, but I can't find a flat stretch of grass. I'll see if rotating the tires solves the sound. And no, the tires are not oddly worn in any way. I almost want to place the rear on stands, run it and see if the noise occurs, but that sounds like an accident waiting to happen.

Don't want to have this happen. Jump to 1:30

You Tube

You Tube

Reply 6 : Low Hum Sound

Quote:

Originally Posted by musubi I'll see if rotating the tires solves the sound.

If the tires were damaged/worn due to cupping, rotation would have no effect since the damage is already done. If you're not seeing any damage associated with cupping then the issue lies elsewhere as Dark Taco suggested.

Reply 7 : Low Hum Sound

Thanks guys! That site from Dark Taco is really helpful. The hum does kinda sound like it's a "whirring" sound. This gives me a good place to start anyways. Much thanks to all. I'll keep you guys posted, for reference, on the outcome.

Reply 8 : Low Hum Sound

Update:



So, I was in the process of rotating the tires and I found the area where the sound is coming from. It's not the tires. It's the area around and between the two inner CV joints. It could be the bearings or the unit between the inner CV joints (I don't know what it's called. Looks kinda like a transfer case or something?) Anyways, the noise stems from this area and I'm taking it in tomorrow. If the problem is found somewhere along this CV axle, would this be covered under the powertrain warranty? I'm guessing not, but just feeling out people's opinion on this. The dealership will tell me if it is or not, but my trust in this dealership is just not there. The noise sounds like a whirring only when the front driver side tire is rotating.



Appreciate any thoughts on this.

Reply 9 : Low Hum Sound

Sounds like your refering to your front diff. 05moose had his replaced recently this might be worth a read before you go in. Maybe he'll even chime in: Front diff vib link

Reply 10 : Low Hum Sound

Yep, it definitely sounds like the front diff vib. If that is indeed what it is, it should be convered under the 5 yr/60k mile warranty.

Reply 11 : Low Hum Sound

Thanks guys for your replies. Turns out, it was the bearings causing the sound. Maybe my description of the sound was off. It was covered under warranty and now all seems to be better. I have a hard time believing the bearings went out so soon, but I'm glad it turned out to be the bearings instead of a diff or trans. The work was done fairly quickly and of course free. Thanks everyone for your help in the diagnosis.

Reply 12 : Low Hum Sound

Wheel bearing or was it a diff bearing?

Reply 13 : Low Hum Sound

bump to this. what bearings? tnx.

Reply 14 : Low Hum Sound

I'm gonna guess here and say wheel bearing (hub assembly). I have had both of mine replaced, one around 35K, one at 98K. Symptoms are as described, diagnosis.. turn slightly right, turn slightly left, if it quiets turning right, it's the left one and vice versa. I also replaced 3 in our ZR2 trucks and one in our old Bonneville.