High-pitched tone coming from underneath 1996 Limited

[judeOchop]

Hey guys,

I've done a bunch of searches, but can't find anything that quite describes what I'm hearing on my (new to me) 1996 LTD, 151k miles. When running, there is a high-pitched tone that can be lost in the engine noise, and can't be heard in the cab, but is certainly there. I crawled underneath and i _think_ it sounds like it's coming from near the transfer case, but I'm not certain.

It's nothing to do with the radio and the sound only happens with the engine running.

Since it can't be heard in the cab, I'm not worrying about stopping the sound, unless it's indicative of a problem, which brings me to you guys - thoughts?

 

[Troybylt]

Alright let's start the trouble shooting interwebs diagnostical hyper test.
I used big words that sound made up so you can tell I'm a professional diagnostitian.

In all seriosuness now;

It's only heard with the engine running, are you sure? If you are rolling down the road and turn the engine off (put the car in neutral first!) does it make the sound?

Are you manual or automatic? This will determine the next questions.

 

[judeOchop]

Thanks for the reply.

It's an automatic transmission. I first heard it while climbing out of the cab, engine still running, transmission in park. However the tone persists in all gears (at least while not moving, I can't otherwise hear it over the engine/wind noise and I can't exactly get close to the sound when it's moving)

EDIT: and of course it turns off when the engine is off.

 

[Troybylt]

Alright Auto! Whee! AND that's why I searched far an wide for a stick!

ALright Let's see if we can narrow it down, it's an auto so I would think that it would not be the transfer case as the transfer case is down stream in the drive line and if the Auto trans is in park or neutral it should not be spinning the output shaft.

Which means it's probably in your transmission.

First and easiest to check is your transmission dipstick to see if your fluid level is correct. It should be either and orange ring or a red T-handle or something like that further back than the black or yellow oil dipstick. If all is well there move on to step two.

Second thing I would check is the radiator to see if it's full of pink foamy gunk. That would be your transmission fluid contaminating your radiator coolant and vice versa THE DREADED PINK MILKSHAKE! if your not familiar a quick search should keep you from sleeping at night.

Let me know I'll be around here for a while.

 

[judeOchop]

Yeah, I lurked a bit in this forum before I bought this car and knew the pink milkshake can be a looming shadow.

I can't check the trans level right now - but I feel pretty good that it's not the pink milkshake, I was checking out the radiator a few days ago and it was not at all foamy (though it is red - which freaked me out until I learned about Toyota red antifreeze...)

When I get out to my truck this evening I'll give it another listen, check the trans level, and try switching 4WD on/off, see if that makes any difference.

 

[Troybylt]

Hrm, that makes an interesting puzzle then, it makes the noise whether it's moving or not. Sounds can be funny and travel through metal very well, listen carefully with the hood up to see if the sound isn't coming from a pulley in front.

If not try the fallowing:

I would check the Trans and Coolant like I said and add check the oil level, maybe even add an oil change, and transmission fluid change search to find out what the auto tranys like. For instance Redline GL4 MT-90 is like magic sauce for manual trannys, there may be an equivalent for the auto.

Most high pitch constant wining noises are going to be something that is always turning like the pulleys up front or the bearings in the transmission. If the truck is in 2Hi the transfer case really shouldn't have anything turning in it while the truck is parked so I would all but eliminate that and trouble shoot the transmission.

Does the frequency or pitch change as your engine speeds up in park? Does it change when the vehicle speeds up or slows down? Is it more noticeable in different gears?

If you set the parking brake or hold the brake down and put the truck in gear does it still make the sound? Does it make the sound when you foot is holding the brake down firmly and you apply light throttle? (this will bog the motor a bit) When doing this is there any change in frequency or pitch?

Going to take off for a while but hopefully that gives you some stuff to try or think about, will check back up on this thread later tonight.

 

[judeOchop]

well, I've done a bunch of different things - no real results though. Turned on 4WD, engaged neutral and 4Lo, park, reverse, it's ever-present. I don't see any issues with the trans fluid or oil. I can't tell if the tone gets higher pitched at higher revs because engine noise drowns it out.

My best guess for where it's coming from is the actuator on the rear diff. I tried to get a recording of it, but I honestly don't know if anyone else can hear it. I'd almost believe I was imagining it, except i can definitely notice the difference when the car is shut off. It's the highest tone in the clip, most noticeable towards the last few seconds (I moved my phone closer to the actuator).

But I could very well be in the "getting to know you" phase of this relationship, and every little thing is making me nervous. There are some things that should probably worry me more, like there is something like a chatter when getting up to highway speed (valves? exhaust leak?), I don't think my MPGs are great (car is still new enough I haven't even done a full tank through it yet but i've got about 200 miles on ~3/4 of a tank), etc... Everything else about the car seems really clean, just some quirks to figure out.

Lots more reading to do! Thanks!

 

[Troybylt]

Have to say I listened to the recording even on my bose headset with the bass tuned out, I'm hearing no whine, nothing man just the engine running.

It may just be "one of those things". Our trucks do have a lot of personality, and with that comes quirks.

If you think it's coming from the 4WD diff actuator try changing the breather out with a new part and doing a diff fluid drain and fill with new synthetic fluid. It may help queit things up. It could just be time to change the lube. I belive a few guys on here were able to quiet up a old diff with some thicker than stock Royal Purple gear oil, apparently that stuff is pretty sticky and thick.

If you have a chattering (Kinda sounds like maybe a heat shield is loose or something rattling under acceleration) and a check engine light it's probably the Mass Air Flow Sensor, it pretty much has to be replaced with a Toyota OEM part as the truck is really finicky with non OEM MAF's.

You can hear what I'm talking about briefly at :57-59
https://www.youtube.com/watch?v=V8oEfk5jVSI&feature=youtu.be

When I first got my truck it chattered quite a bit under acceleration getting up to speed, was a bit underpowered and had CEL for p171 I believe. A new MAF ($170 from the dealer I believe, was a while ago) fixed the check and what I thought was a rusted and loose heat shield noise COMPLETELY went away. The above video was taken while wheeling the day after I got it. Couldn't go the day I got it as it had metal to metal brakes and ZERO tread. (Showing belts) So I brought her home did the 199mm Tundra upgrade and drove it to the tire shop to wrap up in some BFG AT's by then it was too dark for me to wheel comfortably. Last thing I wanted to do was break down in the dark in the mud far away from home. So when the sun came up the next morning...

Best of luck for you and your new truck man, if you got anymore questions I would be happy to scratch heads with you.

 

[Teedeejr]

High pitched whistle - whine

Thanks for the reply.

It's an automatic transmission. I first heard it while climbing out of the cab, engine still running, transmission in park. However the tone persists in all gears (at least while not moving, I can't otherwise hear it over the engine/wind noise and I can't exactly get close to the sound when it's moving)

EDIT: and of course it turns off when the engine is off.

Thought I'd bump this thread, cause out of all of the threads I've read this sounds closest to what I'm dealing with

https://m.youtube.com/watch?v=Gdu4BbPkWnQ&feature=youtu.be

Stats in truck - 1998 SR5 - auto 3.5 V6 - regular emissions- 124K. Purchased 2 1/2 months ago - I didn't hear this noise when I purchased - it was also much hotter than it is now (not that it's cold in Louisiana now, but much cooler).

I don't hear the noise immediately upon starting but after a 25 minute commute sometimes it's pretty loud. Really doesn't change pitch or frequency - is there in all gears - neutral and park, when accelerating and braking. I thought it might be a vacuum leak as I've got a persistent P0171 code.
New after market MAF - the code was there before and after, cleaned the TB - swapped a vacuum hose and replaced the PCV valve, grommet and hose.

Sometimes it seems a little lower but never goes away.

Any ideas are appreciated - I'm starting to hear the whine even when the truck
Is turned off...

 

[19963.4lsr5]

It could be your fuel pressure regulator causing the 171. And may be the source of the noise. The high pitch sounded clearest when you were at rear of engine. The code refers to the system running too lean. It's having to add too much extra fuel to compensate for a problem. Low fuel pressure is one of the causes. Or the filter is clogged and the pressure regulator under the intake has its spring almost all the way closed to try and bring up the pressure. Or your pump is going bad. Filter is easiest and most logical to replace without the stuff necessary to test fuel pressure at the fuel rail, and between the filter and regulator.


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[rubegoldberg]

currently experiencing this with my camry, so figured i'd mention it.

had a loud whirring coming from the engine, put my ear to the engine, discovered it was the alternator bearings going.


took it to my shop to confirm, turned out to be the AC compressor.

 

[19963.4lsr5]

currently experiencing this with my camry, so figured i'd mention it.



had a loud whirring coming from the engine, put my ear to the engine, discovered it was the alternator bearings going.





took it to my shop to confirm, turned out to be the AC compressor.

He could pull the belts off and run engine and see if noise is still there or not.


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[Teedeejr]

Update this morning - 40 degrees out - drove about 5 minutes - 2 miles and when I got out there was no whistle.

30 minutes later I get back in and start it and the whistle is there.

Ive got an plug in Obd2 scanner and use OBD Fusion app, but I'm not sure that will say much about the fuel rate.

 

[johnbyebye]

Update this morning - 40 degrees out - drove about 5 minutes - 2 miles and when I got out there was no whistle.

30 minutes later I get back in and start it and the whistle is there.

Ive got an plug in Obd2 scanner and use OBD Fusion app, but I'm not sure that will say much about the fuel rate.

I had the same noise in the video you posted earlier on my Chevy. It turned out to be a crack in the exhaust manifold that was sucking air in. Surprisingly no codes or anything. Check 'em just to rule them out if you haven't already.

Cheers.