High pitch noise

[mamankyle]

Hello,

I was on a long drive yesterday on the interstate in my 69 170 3 speed when I noticed a high pitched "whistle", when I slowed down and there was less wind noise the "whistle" did not get quieter, it remained at the same pitch until about 2 miles an hour and then it stopped abruptly, before the car stopped. And the noise was from something turning. I know very little about these cars and am learning all of time, would the drive shaft cause this? I checked it and there is no play, very tight. The rear differential is stock, and there is a 1.5"lift block in the rear that was there when i bought it. Would the block change the angle of the driveshaft to ther differential? Any help would be appreciated.

 

[73Russell]

Where did the whistle sound like it was coming from?

 

[rhinobuggie]

Everytime you call a Bronco a car a kitten die's

 

[blubuckaroo]

Everytime you call a Bronco a car a kitten die's

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[SHX669]

I suspect the radiator cap " blowing off "excess pressure or a vacumn leak. Maybe the PCV valve or hose to it.
i know very little about the 6 cylinder motors. But a drivetrain issue would change both in volume and frequency as you changed speed and things turned faster or slower.
SHX

 

[DonsBolt]

did it sound like it was comming from the engine somewhere, or from the rear of the truck??

Thats a wierd one, as anything in the drive train, a alternator, powere steering pump, water pump would all change with either engine speed, or wheel speed.

Was it more of a whistle or a squeeling noise?? A whistle would lend me to think, vacuum leak, or carb. A squeeling noise, a belt, alternator, or waterpump

 

[mamankyle]

It is more of a whistle. I thought of a vacuum leak, but it sounds like it is turning when i slow down, then it sounds more like a squeel, or metal on metal sound. But it stops before the the car stops moving. The alternator is new, no power steering. Even weirder is it did not make the noise this morning on my 15 mile commute. I will check the hoses, but the fact that it is definately a tgurning noise would preclude that. It sounded to me in the drivers seat that the noise was comming from the passenger rear, but my friend in the passenger seat said it was coming from transmission area.

 

[73Russell]

sounds like it may be a ujoint going out. Mine were tight but no good when I removed them.
is the tranny and transfer full?

 

[blubuckaroo]

When I look for noises I have someone walk along to locate it. Then put it on blocks and run it.

 

[73stallion]

do you have disc or drum brakes? i'm thinking wear indicator on the brakes if you have disc. my prelude is doing the same thing right now.

 

[SHX669]

I've also found rocks and broken springs inside the drums .
They'll make a noise similar to what you describe . Pull the drums off .
SHX

 

[commoncold]

The quick way to cehck your drivetrain is this:

-Put in neutral and rev the engine to see if it reappears (lets you know if its in the engine or not)
-Roll down a hill in neutral (lets you know if it is in the tranny/transfer case/driveshaft/differential)
-Roll backward down a hill in neutral (lets you know if it is the brakes, if it is you should either not hear it or it is more quiet)
-Try putting transfer case and neutral and rolling (driveshaft/differential)

I would agree with others that say radiator cap letting off. That is about the closest noise to a high pitched whistle as you can get. look for water around the radiator cap.

I think a big question to ask is whether the noise increases/decreases in pitch or volume when changing speed, gears, or engine rpm?

 

[mamankyle]

The sound went away for about 2 weeks then reappeared on a 300 mile trip. It was very loud. The noise is not related to speed, it is always the same pitch. When the truck is in neutral rolling it remains the same pitch as when it was in gear. It's not the radiator, as it has definite "turning" noise like a driveshaft. It stops at about 3mph. I have not tried putting the transfer case in neutral and rolling, I wil try that. and the rolling backward. The problem is the sound disappeared the next morning, or more probably it is just quieter. Maybe the longer drive and the heat is causing it.

 

[stock1970]

i have a similiar noise in my stock 70, but when i stop i notice a almost howling noise, then if i rev the engine up a little it goes aways and it is not consistance.. sometimes there and some times not.. i dont have pwer steering so that is ruled out.. i will try and have someone with me next time mine does it. if i fgure it out i will let ya know.. although my issue may be dif than yours.. i have a 3 on the tree .. so i am thinking something to do with that or sound from overflow sucking i dont know..

 

[mamankyle]

This problem has reappeared again, it never really went away, had other problems to deal with. After about 6 miles of continuous driving it is very noisy, making the same decibel level regardless of speed, until about 2 mph then it disappears. It does not make the sound in reverse. What would make a high pitched sound, not be affected (in decibel level) by the speed, and then quit at 2 mph? A bearing in the driveshaft?
I might be forced to spend some $ on a mechanic......

 

[mamankyle]

In response to Commoncold:

Put the car in neutral and revved the engine, noise is still there.
Rolled down a hill in neutral, noise still there.
I will check it in different gears in the transfer case today. It is not the radiator, as it is clearly a noise from something turning, and it stays the same noise level regardless of speed, no noise in reverse.

 

[W650Mike]

Roll down the hill in neutral again first with the engine running, and then repeat with the engine off. Repeat the procedure (engine on/off) with the transfer case in different gears.

Let us know what you hear.

 

[Ohio Bill]

Since you have a 3 speed tranny I would guess it to be the pilot bearing.

 

[d.c.parris]

could also be the throwout bearing riding on the clutch fingers

 

[mamankyle]

Thanks. I'll try that.