Mystery drivetrain noise help! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Korr053 · 05-01-2009, 09:23 PM

Hi, I have a 71' C30 dually that has me and all my shadetree buddies stumped.
The problem is when driving I'm getting a terrible howl/grinding/scream from somewhere in the drivetrain. (I think) The noise isn't bad in low gears but when I get into fourth and get going 45-55 it screams. When I press in the clutch it stops. I replaced the tranny, a sm420, and the clutch with no luck. Dosn't sound like the rearend, any ideas? Thanks!

mikajo39 · 05-01-2009, 10:28 PM

I would take a look at your U joints, they can cause a screaming/howling noise if they go bad

chas350 · 05-01-2009, 10:32 PM

curious, did you replace the throw out and pilot bearings?
carrier bearing maybe?
does the sound change when you let off or step on it while cruising?
could be the rear, they can really howl.

powell72 · 05-01-2009, 10:38 PM

Since it goes away when you push the clutch in my first thought would be throwout bearing.

**Boog** · 05-01-2009, 10:57 PM

I'd be sure to drain the rear end and look the oil over real good. It probably needs changing anyway. Sounds from the rear end can travel up the driveshaft and sound like they're coming from somewhere else.
Can you put it up on jack stands and make it do this?

Korr053 · 05-01-2009, 11:09 PM

Yup we replaced the throwout and pilot bearings. (they were shot)
It still makes the noise when i let off but not as bad. And it gets worse the faster I go, but dosn't seem to make a difference if I romp on it at 55.
The driveshaft was tight going onto the tranny if that might make a difference I thought it should have had more play in it.
Ya I'm thinking we need to put the rear end off the ground and go over it from the tranny back to rear end.

larry may · 05-02-2009, 08:28 AM

Is the clutch disc faced the right direction. as in is it flipped 180 degree. I sen this in a vehicle once.that resymbles the description you describe.

Korr053 · 05-02-2009, 04:15 PM

OK!
We put the rearend up today and found the problem! The rear end is shot. I put a magnet in the rearend and got alot of metal, big nuggets. Thanks for all your ideas!

69halfton · 05-02-2009, 06:04 PM

good to see you found your problem!

btw, welcome to the board!

05-01-2009, 09:23 PM	#1
Korr053 Registered User Join Date: Apr 2009 Location: cedar rapids, IA Posts: 3	Mystery drivetrain noise help! Hi, I have a 71' C30 dually that has me and all my shadetree buddies stumped. The problem is when driving I'm getting a terrible howl/grinding/scream from somewhere in the drivetrain. (I think) The noise isn't bad in low gears but when I get into fourth and get going 45-55 it screams. When I press in the clutch it stops. I replaced the tranny, a sm420, and the clutch with no luck. Dosn't sound like the rearend, any ideas? Thanks!

05-01-2009, 10:28 PM	#2
mikajo39 Gearhead and audio junkie Join Date: Aug 2008 Location: nunyah Posts: 452	Re: Mystery drivetrain noise help! I would take a look at your U joints, they can cause a screaming/howling noise if they go bad

05-01-2009, 10:32 PM	#3
chas350 Registered User Join Date: Mar 2007 Location: Connecticut Posts: 581	Re: Mystery drivetrain noise help! curious, did you replace the throw out and pilot bearings? carrier bearing maybe? does the sound change when you let off or step on it while cruising? could be the rear, they can really howl. __________________ "I'll Procrastinate Tomorrow" quote by LEEVON 71 K10 long fleet (sons truck) new 370hp 355, sm465 np205, 3.73's 33's 70 K20 long fleet 98 G3500 work van

05-01-2009, 10:38 PM	#4
powell72 Senior Member Join Date: Jan 2005 Location: Loveland Co. Posts: 3,098	Re: Mystery drivetrain noise help! Since it goes away when you push the clutch in my first thought would be throwout bearing. __________________ Chris 74 Custom Deluxe SWB 350/350/3.73’s 99 2wd Silverado RCSB 5.3/4L60/3.90’s http://www.classictrucks.com/feature...short_bed.html

05-01-2009, 10:57 PM	#5
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,514	Re: Mystery drivetrain noise help! I'd be sure to drain the rear end and look the oil over real good. It probably needs changing anyway. Sounds from the rear end can travel up the driveshaft and sound like they're coming from somewhere else. Can you put it up on jack stands and make it do this? __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

05-01-2009, 11:09 PM	#6
Korr053 Registered User Join Date: Apr 2009 Location: cedar rapids, IA Posts: 3	Re: Mystery drivetrain noise help! Yup we replaced the throwout and pilot bearings. (they were shot) It still makes the noise when i let off but not as bad. And it gets worse the faster I go, but dosn't seem to make a difference if I romp on it at 55. The driveshaft was tight going onto the tranny if that might make a difference I thought it should have had more play in it. Ya I'm thinking we need to put the rear end off the ground and go over it from the tranny back to rear end. Last edited by Korr053; 05-01-2009 at 11:12 PM.

05-02-2009, 08:28 AM	#7
larry may Senior Member Join Date: Jul 2005 Location: MISSOURI Posts: 3,256	Re: Mystery drivetrain noise help! Is the clutch disc faced the right direction. as in is it flipped 180 degree. I sen this in a vehicle once.that resymbles the description you describe. __________________ The biggest problem people have, is other people Thou shalt be cool and not hassle Be a site supporter. The heart of the wise inclines to the right, but the heart of the fool inclines to the left." Ecclesiastes 10:2

05-02-2009, 04:15 PM	#8
Korr053 Registered User Join Date: Apr 2009 Location: cedar rapids, IA Posts: 3	Re: Mystery drivetrain noise help! OK! We put the rearend up today and found the problem! The rear end is shot. I put a magnet in the rearend and got alot of metal, big nuggets. Thanks for all your ideas!

05-02-2009, 06:04 PM	#9
69halfton Registered User Join Date: Apr 2007 Location: King City, Ontario, Canada Posts: 974	Re: Mystery drivetrain noise help! good to see you found your problem! btw, welcome to the board! __________________ - Jason If you can turn, Youre not going fast enough. Favorite caption: first car to 200 mph in the 1/4 mile, no parachute, drum brakes all the way around.. ..back when men were men.



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