Loud Whine - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Zonaman** · 04-09-2017, 11:48 AM

Hi Folks:

I've tried searching this one first but the terms are too generic. I'm getting a loud whine or screech at 4000 rpm. Here's what I know:

* It's loudest under the hood seems like drivers side but I can't pin point it.
* doesn't matter if A/C, fan, or radio are on or off
* does it in any gear or neutral right at 4000 rpm, driving or standing still.
* starts and keeps going hot or cold at 4000 rpm or more, stops as soon as you drop below.
* alternator seems to charging just fine
Got a 350 with a 700r4

Where should I be looking?

Thanks

Money_pit · 04-09-2017, 01:39 PM

Maybe remove the belts and fire it up see what happens from there. Then put one belt on at a time maybe. Just an idea good luck.

arocars · 04-09-2017, 08:44 PM

Most probably the bearing of one of your accessories. When they wear out they squeal.
I agree with prior poster, remove all the belts and reinstall one by one until the sound comes back.
With the belt off, the alternator should spin freely by hand. 8+ spins: good vs. 2 or 3 spins: bad. (Alternators are rebuildable.)
Water pump bearings are usually associated with a leak.
I've never had a power steering pump bearing let go before.
My guess is the AC compressor. I had this happen on a 94 Camaro that I owned. Every week or so I'd give it a shot of WD40 and it would go away for a while.

**Zonaman** · 04-10-2017, 09:23 AM

Quote:

Originally Posted by arocars

Most probably the bearing of one of your accessories. When they wear out they squeal.
I agree with prior poster, remove all the belts and reinstall one by one until the sound comes back.
With the belt off, the alternator should spin freely by hand. 8+ spins: good vs. 2 or 3 spins: bad. (Alternators are rebuildable.)
Water pump bearings are usually associated with a leak.
I've never had a power steering pump bearing let go before.
My guess is the AC compressor. I had this happen on a 94 Camaro that I owned. Every week or so I'd give it a shot of WD40 and it would go away for a while.

Thank you. Just one clarification- the bearing on the AC compressor can make that noise with the compressor off?

arocars · 04-10-2017, 10:48 AM

Yes. There is a clutch built into the compressor. The belt always turns the pulley, but it does not cause the compressor to work until the AC is turned on and the clutch activated.

**FleetsidePaul** · 04-10-2017, 11:00 AM

I had a loud whine in my truck too.

But I just told her to go back in the house.

weq92f · 04-10-2017, 04:09 PM

I had a similar Whine in my T/A. It was the sweetest gear whine in 1st and 2nd gear ( T56 Trannny ) from about 4k all the way through red line!!!!!

It's a whine I miss on a regular basis.

-klb

RGT · 04-10-2017, 06:14 PM

my truck has a bigger fan than than stock I believe(it has a dual belt pulley on it) and it seemed like no matter how tight I made the single belt that drove it it would squeal when I got up over 3500 rpm or so. I installed a dual belt pulley on the alternator and crank and now run dual belts and have not had any squealing since. and I don't have to have too much tension on the belts.

04-09-2017, 11:48 AM	#1
Zonaman Senior Member Join Date: May 2004 Location: Chandler, AZ Posts: 517	Loud Whine Hi Folks: I've tried searching this one first but the terms are too generic. I'm getting a loud whine or screech at 4000 rpm. Here's what I know: * It's loudest under the hood seems like drivers side but I can't pin point it. * doesn't matter if A/C, fan, or radio are on or off * does it in any gear or neutral right at 4000 rpm, driving or standing still. * starts and keeps going hot or cold at 4000 rpm or more, stops as soon as you drop below. * alternator seems to charging just fine Got a 350 with a 700r4 Where should I be looking? Thanks __________________ 69 C-10 LWB, 350, 700r4, 3.73 posi-traction, front disc brakes. Built for the desert- She can take the heat! Vivat Rex Chevus!

04-09-2017, 01:39 PM	#2
Money_pit Registered User Join Date: Jan 2014 Location: Illinois Posts: 131	Re: Loud Whine Maybe remove the belts and fire it up see what happens from there. Then put one belt on at a time maybe. Just an idea good luck. __________________ 71 C10 Finally took a leap and did the 5.3 4l80e swap. Running the Holley Terminator Xmax. Still working bugs out.

04-09-2017, 08:44 PM	#3
arocars Registered User Join Date: Dec 2010 Location: Taunton, Massachusetts Posts: 26	Re: Loud Whine Most probably the bearing of one of your accessories. When they wear out they squeal. I agree with prior poster, remove all the belts and reinstall one by one until the sound comes back. With the belt off, the alternator should spin freely by hand. 8+ spins: good vs. 2 or 3 spins: bad. (Alternators are rebuildable.) Water pump bearings are usually associated with a leak. I've never had a power steering pump bearing let go before. My guess is the AC compressor. I had this happen on a 94 Camaro that I owned. Every week or so I'd give it a shot of WD40 and it would go away for a while.

04-10-2017, 10:48 AM	#5
arocars Registered User Join Date: Dec 2010 Location: Taunton, Massachusetts Posts: 26	Re: Loud Whine Yes. There is a clutch built into the compressor. The belt always turns the pulley, but it does not cause the compressor to work until the AC is turned on and the clutch activated.

04-10-2017, 11:00 AM	#6
FleetsidePaul R.I.P. E.S.L.L. Join Date: Aug 2005 Location: Kernville CA./ Lake Isabella CA. Posts: 11,419	Re: Loud Whine I had a loud whine in my truck too. But I just told her to go back in the house. __________________ 1971 Custom C/20 1970 CST 20 1970 C/30 Flatbed 1983 C/30 Dually 2015 Corvette Z51 2021 Corvette Z51 1991 Cadillac Hearse 1982 Cadillac Eldorado Biarritz 2000 Porsche Boxster S 2020 Jeep Gladiator 1973 VW Thing 1973 Plymouth Satellite wagon 1963 Baja Bug 1959 Bug Dune Buggy 1970 Baja Bug 1987 Jaguar XJ 350. R.I.P. El Jay R.I.P Jessie. R.I.P Grumpy. Every day is a gift from God.

04-10-2017, 04:09 PM	#7
weq92f Registered User Join Date: Oct 2016 Location: Dallas Texas Posts: 3,010	Re: Loud Whine I had a similar Whine in my T/A. It was the sweetest gear whine in 1st and 2nd gear ( T56 Trannny ) from about 4k all the way through red line!!!!! It's a whine I miss on a regular basis. -klb __________________ 67 C10 fleet fuel injected '70 402, 700r4, 3.73 posi 07 335 sport turbo 6sp 94 Trans Am GT LT1 6sp posi -- sold after 22yrs 99 540 sport V8 6sp -- sold 73 240z L24 4sp -- given to friend 68 C10 step 350/350 3.73 open -- sold

04-10-2017, 06:14 PM	#8
RGT Registered User Join Date: Mar 2016 Location: Portsmouth, NH Posts: 45	Re: Loud Whine my truck has a bigger fan than than stock I believe(it has a dual belt pulley on it) and it seemed like no matter how tight I made the single belt that drove it it would squeal when I got up over 3500 rpm or so. I installed a dual belt pulley on the alternator and crank and now run dual belts and have not had any squealing since. and I don't have to have too much tension on the belts. __________________ 1971 C10 long bed, fleet side. 200R4 Auto, leaf spring rear. power steering.



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