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Old 08-13-2014, 02:39 PM   #1
adricar1
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whiring noise when decelerating?

I have just started to have a noise when i accelerate very slowly and driving at 1500-2000rpm. When i decelerate when the engine is warm the noise is greater. I have checked the fluid in the th350 and is slightly over filled. the th350 was rebuilt 300 miles ago, and everything checked out ok. transfer box rebuilt again and seams quiet. I have noticed play in the sliding joint on the front drive shaft? would this be causing the noise?
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GMC K1500 1971 350 cu in th350 4wd
Bondo Bob c 10 1971 stepside th 350
c10 1970 350 cu in manual air con stepside.
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Old 08-13-2014, 09:18 PM   #2
Tango59
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Re: whiring noise when decelerating?

Maybe wheel bearings or u-joints.
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Old 08-13-2014, 10:20 PM   #3
davepl
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Re: whiring noise when decelerating?

Could it be the clutch fan?

There should be no play in the u-joint. It's a slip yoke design so it can slide in and out, but there should be no rotational slop in the setup. Even if that's not the cause of the sound, you'd want to fix that if true.
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Old 08-14-2014, 09:35 PM   #4
hotrodder
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Re: whiring noise when decelerating?

might be the pinion bearing, had that same kind of sound on my 63.
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Old 08-14-2014, 10:03 PM   #5
Tango59
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Re: whiring noise when decelerating?

My 69 makes the noise on acceleration... letting off the throttle it stops... I'll probably do all the bearings in the rear after some OT at work this fall.
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Old 08-17-2014, 10:16 AM   #6
adricar1
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Re: whiring noise when decelerating?

checked the wheel bearing on the front and noise still there,i have changed the rear bearing on the 12 bolt just to be sure but there was not any noise from the back axle? the noise is there when coasting in neutral so could i rule out the th350 as a possible cause? u jints on rear prop have been changed. and new clutch fan . i am running out of ideas.
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GMC K1500 1971 350 cu in th350 4wd
Bondo Bob c 10 1971 stepside th 350
c10 1970 350 cu in manual air con stepside.
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Old 08-17-2014, 12:28 PM   #7
adricar1
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Re: whiring noise when decelerating?

just tried the engine with the rear end on axle stands and the noise is coming from the transmission. it seams as if its the bearing in the adaptor plate between the th350 and transfer box? does anyone have a part number for this bearing?
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GMC K1500 1971 350 cu in th350 4wd
Bondo Bob c 10 1971 stepside th 350
c10 1970 350 cu in manual air con stepside.
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Old 08-18-2014, 01:55 PM   #8
Tango59
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Re: whiring noise when decelerating?

Not sure if this is the same but try this link http://www.partsgeek.com/catalog/197...t_bearing.html

Good idea putting it on jack stands and listening....
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Old 08-18-2014, 02:22 PM   #9
adricar1
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Re: whiring noise when decelerating?

apparently i have been told that they stopped fitting the bearings on later models. so tomorrow i have afriend coming around, and we will disconnect the propshaft and get the stethoscope out to track the noise down.
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Bondo Bob c 10 1971 stepside th 350
c10 1970 350 cu in manual air con stepside.
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