I bought mine from NJ636 and couldn't be happier. Look him up.
Sorry to bump this thread but this was the closest thing I could find to describe my current situation.
I bought a used 2007 4Runner Limited 2WD with 130k miles on it. Got a great deal on the truck and didn't have a lot of choices after my wife stole my Forester and I was stuck taking the kid to school or picking up in a 2 door coupe.
I was driving around about a month after purchasing and I noticed the same exact thing - I would hear a hum, a little higher pitched than road noise from the tires, coming from what sounds like the middle/rear of the truck. The best way to describe it is downshifting from 4th gear to 3rd gear in a manual transmission. Kinda like a quieter, duller sounding hum reminiscent engine braking in my old Honda Civic.
Couple things:
- The noise isn't really audible between 0-30 mph. I can only hear it above 30 mph, it gets louder if I'm going down a good sized hill and I'm gaining speed.
- If my foot is on the gas at all, the noise isn't audible., and not because the engine noise is hiding it. When I let off the gas, I can hear it after about a half second. It almost feels like it is downshifting.
- The transmission in this truck seems like it's in great shape. It doesn't slip or appear to have any mechanical issues that I can tell.
My cousin is a used car mechanic and I had him sitting in the back seat earlier yesterday and he said he didn't sound like the rear diff. I really don't want to deal with doing wheel bearings on both sides if it's the u joint or rear diff that is causing the sound. He said it's could also be the driveshaft bearing / u joints.
I'm going to try driving it around in my office parking lot to see if turning the wheel left or right makes it go away.
[MENTION=125668]krevo81[/MENTION],
First of all, WELCOME to T4R.org, from another Texan! Second, it's a little difficult to tell, from your desription, if you are having a wheel bearing issue. So, let me give you the tell tale signs and you can better judge. With 4Runners, it is almost always, the front bearings going bad, long before the rears, so the sound should be coming from the front wheels. Also, a bad bearing will sound similar to a propeller driven airplane type of hum. The hum will get noticeably worse, the faster your wheels spin, NOT proportional to engine RPM. Meaning, regardless of whether or not your engine is in neutral, or even running for that matter, if the wheels are spinning fast, you will hear the hum. Another way to verify a bad wheel bearing is to jack up your Runner so that the suspected wheel can spin freely. Remove the wheel and grab the hub assembly and push/pull it. If there is any movement/play, the odds are good that the wheel bearing is shot.
You mentioned that the sound seemed like it was coming from the middle/rear. I would be inclined to have the output shaft bearing checked. Anyway, hope that helps!
2015 TRD Pro here. Seems like most of you have older vehicles, but I am experiencing the same humming noise when I go about 40 mph, started when I had around 7500 miles. It only happens sometimes though, especially in the morning for some reason, so I really hope when I take it to the dealership they will hear the noise.
Replacing the wheel bearing sounds like a common solution, glad to know some of you have been able to fix the problem.
If the noise changes while turning, I would check wheel bearings. Lift the truck with jack's or hoist put transmission in neutral and spin each wheel at a time by hand and listen. The worst wheel will give you different noise than the other, or try to move lifted tire side to side, up and down. You should not have any play, at the same time you will find out if you have any other worn ball joints bushings etc.I think I'm having the same problem now. There's a strong hum and some vibration coming from the front end. It goes away if I turn slightly right. It's proportional to wheel speed, and it doesn't seem to matter if I'm in neutral or drive. I have a V8, so I can't try 2WD. It's worst around 60-65mph. I have 110,000 miles on it.
I plan to check the front diff oil since I never changed it. If it looks dirty I'll change it, but the transfer case fluid looked perfect when I changed that. I think the dealer changed all the gear oil for the previous owner once or twice.
I just had the tires rotated and balanced, and that didn't help the problem. My tires are Michelin LTX M/S2, so they are quiet.
How can I tell if it's a wheel bearing, front diff needle bearing, or maybe the gears in the front diff, or something else? I'll try lifting it up and rotating the wheels by hand, but will I be able to feel the problem that way? Or can I look at the bearings and visually see if they are bad? I don't know what I'm looking for.