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Old 06-03-2016, 07:29 AM   #1
Ed F
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High pitched hum

My '70 is developing an intermittent high pitch hum. It's not a squeal. It is drive line related not rpm related. Doesn't matter what gear it's in (3 speed manual) or if the clutch is in or out. Doesn't do it under acceleration. More often hear it when slowing down. Front wheel bearings are good. Iam wondering about drive shaft bearings or u joint. Any input would be appreciated.
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Old 06-03-2016, 08:01 AM   #2
70STOVEBOLT
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Re: High pitched hum

Any vibration with the hum?
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Old 06-03-2016, 08:37 AM   #3
n33k0
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Re: High pitched hum

Check the fluid in the differential. I had a leaky cover and when the fluid got low it would make noise, most notably when at low speed or decelerating.
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Old 06-03-2016, 04:46 PM   #4
Ed F
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Re: High pitched hum

No vibration. I know the differential was full a year ago and I haven't seen any leaks, but will check that and the transmission.
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Old 06-03-2016, 09:56 PM   #5
70STOVEBOLT
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Re: High pitched hum

Typically if the noise is only under deceleration, it signals a problem with the differential.
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200,000 Mile Club
Disc Brake Club

Owner installed options:
Front Sway Bar
Power Steering
Power Brakes
Cigar Lighter
Courtesy Lights
Deluxe Side Markers
Wiper Delay
Sliding Rear Window
Power Windows
Power Locks
Sniper EFI

2015 Silverado 1500 LS 4.3/6L80/3.23 lowered 2" front & rear
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Old 06-03-2016, 10:36 PM   #6
jocko
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Re: High pitched hum

Could be Neil Young.
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Old 06-04-2016, 03:12 AM   #7
El Dorado Jim
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Re: High pitched hum

Quote:
Originally Posted by 70stovebolt View Post
typically if the noise is only under deceleration, it signals a problem with the differential.
x2
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Old 06-04-2016, 01:35 PM   #8
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Re: High pitched hum

For the cost involved I'd replace the 3 u-joints and steady/carrier bearing. If the noise still persists then I go into the diff.
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Old 06-04-2016, 10:24 PM   #9
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Re: High pitched hum

Quote:
Originally Posted by jocko View Post
Could be Neil Young.




I agree with 70Stovebolt
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