Please help me identify this drivetrain noise...going crazy (2 Viewers)

[NJGX470]

I drove about 1,200 miles on a recent road trip. After about 600 miles to the destination I started getting a noise right at 40 mph, with a slight vibration. It starts at 40 and then continues up until highway speed. Constant slight humming, depending on vehicle speed, not RPM. For some reason it is way more prevalent at 40 MPH than 70 MPH. It almost sounds like the tires are humming or a bad wheel bearing. It will make noise at 40 MPH even if I am in neutral. If I am going 40 MPH and turn sharply right to unload the passenger front tire it will stop. I could have sworn it was the wheel bearing so I changed out both fronts today. Was super disappointed when I finished, took it for a ride, and noise was still there. I also rotated the tires, no change.

Before I went on the road trip I did change out the transmission fluid. Pump out style from the tranny cooler. I have done this before on my 3rd Gen 4Runner so I am familiar with the process, it went smooth. I also changed out the passenger side CV axle as well. I have already tried installing another passenger side CV axle so I believe I ruled that out already. Also I had no noise when I left for the trip, only when I got there it started.

What else can I check here, it is driving me crazy. It is possible that it may be the tires, I thought that by rotating them there would be a change but I can't tell if there was a change. I have Cooper discoverer AT3 4s tires, one size up from stock.

 

[Rednexus]

Are your tires higher in mileage? ATs will start making more and more noise as they age - mine are getting around 40K now and are definitely louder. Seems unlikely it's the transmission, but did you do the final fluid level check at the end via the FSM procedure (get to temp and pull the level check plug?).

Rear wheel bearings in these can also make noise too. I'm thinking mine are on borrowed time at 175K - it seems most start to die around the 200K mark for the 120/150 platform and corresponding 4Runner rigs, all of which share the same rear bearings. It might be worth taking a look at one of them as well.

My money is on general tire wear/noise or the rear bearings.

 

[NJGX470]

Are your tires higher in mileage? ATs will start making more and more noise as they age - mine are getting around 40K now and are definitely louder. Seems unlikely it's the transmission, but did you do the final fluid level check at the end via the FSM procedure (get to temp and pull the level check plug?).

Rear wheel bearings in these can also make noise too. I'm thinking mine are on borrowed time at 175K - it seems most start to die around the 200K mark for the 120/150 platform and corresponding 4Runner rigs, all of which share the same rear bearings. It might be worth taking a look at one of them as well.

My money is on general tire wear/noise or the rear bearings.

I got the tires in September of 2021, so I have been running them for a little over 2 years now. I am kind of unsure about how many miles are on them...maybe 35K or so. It was just weird that all was quiet, or I thought it was, and then after that big 600 mile day I started noticing it. I currently have about 122K on the truck.

Yes I did get the trans up to temp and adjust the level through the check tube..

You are right about it maybe be coming from the rear...it is hard to tell when in the truck. It is odd that the noise subsides when I swerve the truck in one direction, but that could be the tires too I guess. As I previously said I did just do the front wheel bearings, the same thing can happen with the rear bearings right? If I turn in one direction and unload that side the noise could go away correct?

Last night I did do some research and it appears that chasing something like this down is definitely like going down the rabbit hole. I was not aware that these types of noises happen all the time with the 4Runner and GX470. Knowing this I am most likely not going to do anything unless it gets really loud or something becomes obviously broken. I have been wrenching on vehicles for a long time to know that chasing something like this sometimes is not worth the time and effort (annoying noises). It was just nice that this truck was by far one of the quietest vehicles I have ever owned!

 

[Rednexus]

At 35K it could be the tires as they'd be more than half through their life. Mine are just now getting noisy at 40K, though like yours it kind of snuck up on me one day. When I needed front bearings I actually though it was tire noise until it slowly turned into a grinding noise .

Sorry I can't be more help; I'd suggest trying to eliminate the rear bearings as the cause of the noise. I haven't replaced mine yet so I'm not totally sure of the symptoms they make when the start to die - presumably it's not that much different than the fronts.

 

[NJGX470]

At 35K it could be the tires as they'd be more than half through their life. Mine are just now getting noisy at 40K, though like yours it kind of snuck up on me one day. When I needed front bearings I actually though it was tire noise until it slowly turned into a grinding noise .

Sorry I can't be more help; I'd suggest trying to eliminate the rear bearings as the cause of the noise. I haven't replaced mine yet so I'm not totally sure of the symptoms they make when the start to die - presumably it's not that much different than the front.

Thanks for the suggestions. Today I rotated the tires X-style as I noticed the treads were feathering a little. This may have made a little difference, I am not sure. But at least when the tires wear down some opposite the current feathering pattern, maybe it will quiet down some. Than at least I know it's the tires, and not something else.

 

[Jstawgn]

Put jacktand on all 4 corners, lock CDL and run it at the speed you notice the vibration the most.
Use long screwdriver and touch near potential suspect. Make sure to be careful from any running parts.

Potential areas:
1. Driveshaft u joint. As this vehicle become older this often overlooked. Quite a few lost driveshaft lately. It can be catastrophic when fail at highway speed.
2. Pinion bearing of rear differential.
3. Wheel bearing. You replaced front but rear would do the same under cornering load.
4. Transfer case output bearing.