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I'm new to this site so excuse my future screw ups. I have a 77 silverado I recently bought from my parents. It has sat for the last 2 years until a couple weeks ago. Engine is a gm crate 350, and the trans is a t350 with 3/4 ton running gear. I noticed after driving it a few times that it makes a whining/humming sound after I hit about 20mph. I can't pinpoint where it's coming from but it sounds like maybe the trans or tcase. Both are full of fluid and seem to work right. Any ideas on how I can diagnose this issue? Any advice would be appreciated.
 

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I'm new to this site so excuse my future screw ups. I have a 77 silverado I recently bought from my parents. It has sat for the last 2 years until a couple weeks ago. Engine is a gm crate 350, and the trans is a t350 with 3/4 ton running gear. I noticed after driving it a few times that it makes a whining/humming sound after I hit about 20mph. I can't pinpoint where it's coming from but it sounds like maybe the trans or tcase. Both are full of fluid and seem to work right. Any ideas on how I can diagnose this issue? Any advice would be appreciated.

Thank you so much for joining this site we have been waiting for some hardcore tech like this for a very long time.
 

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Thanks for your reply. I am here to learn what I need to do in this case and know that this will be the best place for that. As I said before, any help with this issue is appreciated.
 

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It could be any number of things, wheel bearings, bad u-joint, output shaft bearing going out, center support bearing... A lot of stuff can make a humming noise once you're driving.

To be honest, this section of the forum isn't the best place to ask this question. Hit up General 4x4 or the Newbie forum.
 

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Is the humming sound dependent on engine rpm or vehicle speed? Is it a different tone when your in a different gear at the same speed?
 

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Discussion Starter #9
It seems that it gets to a certain point and maintains the pitch of its sound but sounds almost like it's winding down as I slow to a stop.
 

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Welcome to Pirate. There is a great resource for info in the search box above. Impossible questions are rarely tolerated, you're lucky so far:)
Grow a thick skin, and listen before you talk.


Take a 12pack to your local small mechanic this friday, and have him ride around the block with you. I'm not kidding.


Good luck with the truck, post up what the mechanic says.
 

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Find a way to get it in the air and while a friend has it in drive at the speed the noise occurs at, take a stethescope to the pinion bearings, wheel bearings, t-case, ect. Any crunching scraping ect Is no bueno.
 

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Have you tried hanging from the undercarriage and listening while a buddy drives the truck? That might just solve all your problems.









:flipoff2:


That's a joke. I don't want to get sued.

Seriously, problems like this can be pretty hard to diagnose over the internet, but a trained ear hearing it in person might be able to tell you right off. I like the 12-pack idea. I did it myself once when I needed help and a scan tool to reset the computer/anti-theft nonsense on my car.

Welcome, and don't take anything too personal around here. Search before you post, post in the right place, and don't get too much sand in the vag - it only chums the waters...
 
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