So I don't mean to write a novel here, but I just got my truck back from my mechanic and wanted to give as much background info here as possible. My truck is a 99' Limited with the 3.4 and an automatic transmission and currently has 188k on it. It was dealer serviced its entire life with service intervals every 30k and was a one owner truck until I bought it earlier this year with 175k. It recently started making an occasional whining / humming noise that sounds like it's coming from the center / passenger front driveline. It is extremely sporadic and comes and goes, sometimes louder sometimes its hardly noticeable. For example, I commute 40 minutes away and don't notice the noise at all in the mornings, however when I get off in the afternoon it starts up as soon as I'm driving out of the parking lot. Noise doesn't change reguardless of whether I'm driving uphill, downhill, steering, or have major suspension articulation, or speed. I've had it occur at as low as 5-10mph and as high as 70mph. I usually do all work myself and recently completed a front end overhaul over the summer (new poly lower control arm bushings, SPC uppers, NAPA CV's, Bilstein 5100's and OME 883s, new steering rack bushings and new swaybar endlink bushings) and truck drives great other than this noise it started making a couple weeks ago. I've greased all the ujoints, double checked torque on everything I replaced, checked the driveshaft for slop, checked wheel bearings and tierods for play and didn't notice any play and everything was torqued to spec. The noise goes away when it is in neutral but will occassionally occur when giving it gas reguardless of whether I'm going uphill or downhill.

A couple vids showing the noise when it was most noticeable, its usually quieter than this:
4Runner front end noise pt2 - YouTube
4Runner front end point (pt1) - YouTube

All that said, I have a couple questions:


1.) Does this sound like the transmisson / are there any recommendations for ways to narrow down where this sound is coming from?

2.) When I rebuilt the front with new CV's I ordered two extended length (according to napa) CV axles. One of which ended up being faulty and I needed to get my truck driving again so I swapped in a stock size CV from NAPA on one size, though when I checked both axles next to each other they appeared to be the same length, minus a beefier shaft on the extended axle. Would this affect the front diff / potentially cause this noise?

3.) Are there any recommendations for a Toyota / Japanese specialty shop in the Portland area where I could get a second opinion? Took it to our family mechanic we've used for years, but figured it wouldn't hurt to get a second opinion.

4.) If a bearing is going out, shouldn't it happen as soon as the tranny heats up / more consistently than it currently is? Its odd to me that it doesn't happen during my 40 minute commute to work when the tranny has plenty of time to get up to temp but happens on the way home.

5.) For anyone whose had a similar issue do you think theres quite a while before the tranny goes out (if it is the tranny)? Truck currently drives great and shifts smooth despite the noise, but would like to start saving if a replacement is likely in the near future.

Thanks for reading and any input is much appreciated

I don't hear a whine in your transmission and mine used to have one before it failed earlier this year at 340K. There is some kind of 'moan' (powersteering maybe?) but no trans whine to my ears on either vid. I don't think you have a trans problem, maybe its the crazy front CV axle setup you've got going.

From what I've read, some of the aftermarket suspension products don't have long lives compared to OEM yet I've never used them to really know myself.

Luck.

I also had a transmission fail on my 3rd gen that made a whine, specifically on cold starts. It didn't sound like your videos at all. If you aren't having any transmission issue, I doubt that's where your noise is coming from. Not sure what could be making that noise though.

That to Me sounds more like a fan blower on low going bad.

Or like exhaust shields rubbing.

Another option maybe warn out suspension components that's more like a rubber bushing etc..

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Following- I started getting this same exact inconsistent noise and it's right when I want to put my car up for sale (don't worry, I picked up another one)


My initial thoughts were the U-joints that needed grease - waiting on grease to ship. But since you already done that, that doesn't make me feel better lol




Here's more details on my end, maybe it's the same for you.

-No noise when revving in neutral stand still
-No noise when revving in neutral while coasting
-Noise only occurs when gas pedal is pressed and moving 5mph-70mph
-Noise is VERY inconsistent, will come and go, weather outside temp hot or cold, engine fully warmed up or taking off after a cold start

Thanks for the replies guys. Drove it to and from work again today and had the same thing with it not making that sound and the sound coming back on my way home... I did try switching from drive to neutral when I heard that sound and it pretty much always went away, though I still heard it briefly one time after switching into neutral. That said, wouldn't that narrow it down to something in the drivetrain and not suspension related? I'm kind of wondering if its a bearing in the front diff, a u joint or something with the transfer case as the transmission shifts well and I would think that it would be showing signs of failure if it where starting to go out though maybe that wouldn't be the case if its a bearing inside the trans?

Yep that's literally all the same symptoms I'm having. I'm planning on greasing the ujoints some more this weekend to see if that changes anything, aswell as changing the transmission fluid to see if theres any metal flakes or shavings. Transmission shifts tight and smooth though, so I'm thinking its something else?

Thats what I thought initially, but the noise is there reguardless of whether the blowers (front&rear) are on or off. I'm going to check the exhaust shields this weekend to see if either are loose or rubbing on each other. It shouldn't be a bushing, as the front end has all new bushings unless it somehow sounds like its coming from the front but its in the rear?

Yeah that's kind of what I'm thinking as its shifts super smooth and I haven't had any hard shifts or slipping. Whats weird is sometimes it sounds more front middle and sometimes it sounds like its coming from the back. Its been hard to pinpoint though as its so sporadic.

I'm also kind of leaning toward it being a CV axle issue, I still have my OEM's with torn boots so I'll probably reboot them and try switching them out to see if it changes anything. Both CV's that I put in were the same length which I would assume would be all that matters, but I don't know enough about CV's to say whether or not the thickness would make a difference.

Only thing drivetrain-related not mentioned so far is the torque converter. Don't
know how it would be "tested" though.

Mostly the cv joints clunk and click when full turn. So maybe the issue but probably not.

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I am wondering if they are 100% sure drivetrain related. If it isn't a flex plate cracking. Granted, it's not 100% narrowed down the source yet so it's anyone's guess at this point. I guess it could be a torque convertor.

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I don't know if it's been solved yet, but to me it kind of sounds like a creaking. Maybe like a bushing going bad or needing to be greased?

Or maybe an engine and or transmission mount?

You might have to drop the pan to get a good feel for that, my drained fluid wasn't obviously terrible and my trans was toast, though I did have a filter in the circuit Failed transmission questions
FWIW my trans made noise before failure for a month or so and sounded nothing like yours.

As another reply alluded to straight line intermittent noise doesn't scream CV issue. Rebooting OEM CVs with the boot slide mod (if lifted) has served me pretty well, fyi in case you decide to replace.

It's not the transmission. That isn't what a transmission sounds like when it fails, it's more like a loud "whir" sound that changes with RPM or in my cause, with the torque converter speed at a stop and accelerating from a stop. It sounds more like a rattle than a driveline hum like from a driveshaft. Erratic shifting behavior is the first clue with any transmission problem.

Just for kicks, check your accessory belts to make sure they are tight. It sort of sounds like you get the squeak when you hit the gas? Maybe not though and I'm just interpreting the video wrong. I would put your mind at ease that it's not going to explode and leave you stranded though, it's nothing too serious yet.

Could also be a bad wheel bearing. Do you have any excessive play if you try and wiggle any of the tires when suspended off the ground?

Appreciate all the input, I gave a local shop a call today but they said they wouldn't be able to get it in till next thursday. At this point I'm leaning toward driving it as is and seeing if it worsens/becomes more consistent or possibly taking it into the dealership. The transmission shifts great and I'm pretty sure it isn't the trans but I've never had a trans go out before so I may be wrong. Is there any way to test ujoints without pulling the driveshafts from the truck? I'm somewhat leaning toward it being ujoint related either in the front or rear, though I don't notice much slop in them when driving other than an occasional clunk when switching from reverse to drive despite greasing them recently.

Thanks for the input, I'm also leaning toward it not being transmission related as the trans shifts great and hasn't been hard shifting / slipping at all.
I'll double check the belts as the idler pulley is somewhat noisy though it doesn't sound like its coming from the engine compartment but more from the front suspension or under the vehicle somewhere. Its hard to describe the sound and the video doesn't pick it up that well its more of a whirring / humming noise that almost sounds like excessive tire noise or a wheel bearing. I also thought wheel bearing at first but didn't notice any slop when I checked for play after jacking up all four tires, though I might check this again once its warmed up and the noise occurs. I'm currently leaning towards it being a ujoint or wheel bearing, though it doesn't quite sound like either of those. Really wish I could think of a better way to describe the sound / pick it up in video better...

Appreciate the input, I don't think its CV's and am leaning towards something with the ujoints / driveshaft or possibly wheel bearings. It doesn't sound like a noise torque converter at least from the videos I've seen though I've never had a trans go out. I think I'll reboot the CV's either way as I've seen a couple threads about tolerances being slightly looser with aftermarket CV's and want to make sure its not related to that, though I'm fairly sure its something else at this point.

It might be an engine or transmission mount, but the car was babied (driven by PO's mom) for the 175k miles before I purchased it and I've only wheeled it twice since. I guess they could be starting to wear at this point from age though.

Yeah the sound is hard to describe. My prior 98' I had had a faulty CV so I know what they sound like so I'm kind of wondering if theres slop between the end (not sure of the exact name) of the CV that clicks into place in the spider gear or somewhere else in the diff? Leaning toward it being something else at this point though.

Yeah I wish there were an easy way to test the torque converter. It doesn't sound at all like a noisy torque converter from the videos I've seen on youtube

I'm still following- thought there would be more ideas on what it could possibly be by now . The grease that I ordered for the u-joints should be delivered in the next few days- so much for it being "prime"

It kind of sounds like a mystery noise I chased down on our AWD Sienna. I had replaced a bunch of front end components including wheel bearings and the noise only began after it was warmed up and sometimes slightly affected by turning. I re-replaced that wheel bearing, but the intermittent sound returned and I eventually traced it to the heat shield behind the brake rotor. Very slight interference only when hot and a small hand tweak permanently resolved it. Just thought I'd mention it since you have some thoughts to that region and would be the easiest/cheapest to resolve. Perhaps some slight intermittent rubbing at the end of a CV shaft in the spindle? Have you pried on your LCAs, maybe some bunk aftermarket poly bushings?

If not something weird like that, I follow the "it must be drivetrain" logic. Good luck.