HELP! I've got a metal humming sound

[Ahansen15]

HELP! 99% complete frame off restoration 1972 chevy K20, 402 BB (rebuilt), T400 Auto

Metallic sounding humming sound, constant between the speeds of 34-45ish mph. Does not change with gas pedal or what gear its in.

What's been addressed so far and ruled out:
-Transmission
-Rear-end
-Speedometer cable
-Tires, obviously...
-Open-ended tubes of metal side steps

Anyone had this random problem before, please help!

Thanks,
Asa

[leftybass209]

Welcome!!!

Where is the sound coming from?
Have you had a passenger sit in the truck to help identify where it's coming from?
Have you driven by a wall, or a large flat building? (that helps to isolate a particular side of the vehicle)

When you say you addressed those parts, what do you mean?

An addressed transmission to me, is a 100% iron-clad ruled-out diagnosis, or a complete rebuild.

One thing you can consider doing is buying or borrowing a GoPro camera. Mount it somewhere you think the noise may be coming from, then take the vehicle for a drive. the onboard microphone may help to amplify the sound and isolate the issue.

[StepSide1965]

Hood springs????

[weq92f]

What about Neutral?

Same thing when you free rev to 2500 or whatever 35-45ish MPH translates to in RPM?

If only happens in gear and driving then:

o Front end rotating components ( bearings, drums, etc. )
o link between end of tranny and rear end
o Rear end rotating components ( axles, bearainigs, drums, etc ).

Otherwise, should be easy to find!


-klb