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Weird "harmonic" vibration in '80 Brat


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6 replies to this topic

#1 bratgrl

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Posted 10 June 2007 - 07:51 PM

Okay, I know this is strange, but I have a feeling someone out there will have experienced this, or may know what causes it and if it's anything to worry about.
When I'm going any faster than 65 mph, my Brat makes this weird kind of noise. I've only heard it once before, on my pickup that had a bent driveline, and a cracked transfer case, so it was causing what the driveline repair guy called a "harmonic" vibration. I'm not quite sure how to explain it to you.
If you have a table top fan, when they are running, they kind of change pitch, but the speed it's rotating doesn't change.......so it makes a kinda whirring sound. I hope you get the idea.
The car doesn't shake or rattle or anything like that, it just makes a strange humming noise. I don't know if it's in the motor or what.
What the hell could this be? Is it serious? Is it dangerous? Is something going to fall off the car? Is it going to implode/explode? Am I just going insane and hearing things? Help? :confused:

#2 86BRATMAN

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Posted 10 June 2007 - 10:48 PM

Did the mechanic inspect the u joints. They could be getting slightly worn.

Have you noticed any change in the height of the brat. When my 86 dropped down in the rear from rust it started making a weird vibration and noise similar to this from the change in the angle on the driveshaft

#3 CAS83Brumby

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Posted 10 June 2007 - 10:54 PM

Had the same thing happen on my 79 brat, also on my datsun, also on my toyota, and it was always the u-joints on my driveline, I would have them replaced. Hope this helps. on my 79 it was $90 installed at west bay or you might know it as parts plus.

#4 nipper

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Posted 10 June 2007 - 10:58 PM

Its either the U joints in the driveshaft, or the carrier bearing for the driveshaft. It will get more prounounced with time, but also you will find your top speed slowing down due to the vibration. A simple inspection of the joints will tell.

nipper

#5 86BRATMAN

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Posted 10 June 2007 - 11:00 PM

Hah, I got nipper. LOL. No carrier bearing on these. Straight up one peice driveshaft

#6 nipper

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Posted 10 June 2007 - 11:01 PM

Hah, I got nipper. LOL. No carrier bearing on these. Straight up one peice driveshaft


show off :P

nipper

#7 bratgrl

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Posted 11 June 2007 - 08:52 AM

Thanks guys ! I never even thought of that. I was imagining the worst. I will get the u-joints checked out. Hopefully, it is something that simple. Bobby




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