Humming at 40 mph

My ‘15 Tacoma 4x4 V6 auto trans. has a humming sound at 40 mph which pretty much goes away above 40. Not real loud but i know it’s not normal. Sounds like a mud tire but not as loud. I have highway tires. My first thought was a front wheel bearing but it doesn’t change when you swerve from left to right on the road. Stays the same. Going uphill or downhill the humming stays the same. I changed oil in rear differential and the old oil looked fine. No metal particles or anything. Truck only has 75k miles. I did have transmission flushed and refilled last year at Toyota dealership and had 4 new tires installed ( Dunlop AT 20) Same as came on truck when new. Humming started not long after that. Don’t know if that had anything to do with it. Racking my brain trying to figure out what’s going on. Any help appreciated.

 

I think I have the same thing in my 2017. I hear it whe. I have the rear windows or the back window ope . It is like a mechanical hum — hard to describe and very faint.

 

Yes I thought it might be wind noise but I have ruled that out. I think it’s mechanical because I didn’t start hearing this noise until about a year ago. Really has me stumped. Guess I’ll have to find a good mechanic.

 

Definitely a front Wheel Bearing, I'm replacing mine soon.

 

I’d start where the last changes were made before the hum started. Easier said than done because tires can be expensive and there is no dipstick for our trans. Have you greased your driveline lately? You should have 5 grease fittings on your 4x4.

 

The next time you're on an open section of hiway try a couple of fast lane changes. That'll unload the wheel bearing on one side & if the tone of the hum changes or disappears, you've found the source of the hum.

 

Yes I’ve tried some fast lane changes but couldn’t tell any difference but I’m thinking it’s a wheel bearing. I had a ‘07 Tacoma that had a bad left front bearing and you could definitely hear a difference when making fast lane changes. I have greased all u-joints. Haven’t checked transmission fluid level but assumed they got it right at Toyota dealership when they flushed transmission. Wouldn’t think low fluid would cause humming but it might. I may have to keep driving until it gets bad enough to pinpoint the problem but I know something is not right.

 

have you tried to engage the 4x4 to see if the hum goes away? Or have you replaced the needle output bearing with the ECGS bushing yet?

 

Mine just passed 103k miles and started making a noise like this from 35-40mph. I've had enough cars with bad wheel bearings to know this is a wheel bearing. Added bonus is that it may also be the driver needle bearing as mentioned above. My personal plan is to replace both front wheel bearings (using these) and do the ECGS bushing too so I don't have to worry about it hopefully for another 100k.

 

Yes I agree with you. I think it’s a wheel bearing but what’s throwing me off is that when I swerve from left to right and back to left I can’t really tell any difference in the sound. It stays the same best I can tell. Where is this needle bearing and ECGS bushing you’re talking about? I’m not familiar with either one. Thanks for your help and thanks to the others who have replied to my situation. I would sure like to find the cause of this humming.

 

Search "ECGS bushing" and there will be no shortage of info.... I have done this mod on 2 Tacomas now and would like to add that most claim it appears after lifting the truck, but it was present on my 2015 prior to lifting.... the symptom I had for this issue was a humming that oscillated, but was more pronounced between 35-45 mph..... if you have a constant humming I would lean more towards wheel bearings or driveline carrier bearing....

 

Bearing(s)

 

Thanks for the information. I’m thinking that it is most likely a wheel bearing but I’m going to check that ECGS bushing.

 

Also, check to see if the rubber trim strips on the roof are coming loose. That was an issue in some of the gen 2 models. The strip would begin to come loose at the front where it meets the windshield and would make a vibration/whistling sound as it lifts off the roof from the air.

 

wheel bearing can make noise even without turning wheel side to side...
place veh on hoist (or on stands) place in 4wd and run it up to the speed you hear noise, with a stethoscope or screw driver listen at wheel bearing (just under cv joint) listen to each side if ones bad you will hear it,*** use caution as the wheels are spinning ***

you can also remove caliper/rotor and spin hub by hand you will hear or feel noise as well

 

You said the hum appeared after replacing tires.

Sometimes a new tire will have a cord separation that isn't visible and it will make a noise at low speeds. You could test this by putting the spare on your truck and driving it at the offending speed, one wheel at a time. Is it time to rotate your tires anyway? Just a thought. Chasing a noise can get frustrating and expensive.

 

Thanks for your suggestions. These are some things I didn’t think of. Locating the source of a noise can sometimes be very difficult.