noise issue

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Aug 27, 2022 | 01:28 PM

clayzigler

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From: Missouri

noise issue

I have recently noticed a odd sound while driving my '78. While driving on the highway if I let off of the accelerator I can hear a sound. Not sure how to describe it except maybe a rumble. When I apply the gas the sound goes away. Let off the gas the sound comes back. Does anyone have any ideas before I take it in for service? It's an automatic by the way.

Aug 27, 2022 | 01:33 PM

MelWff

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Is the sound coming from the back?
when is the last time you checked/changed differential fluid?

Aug 27, 2022 | 07:57 PM

4-vettes

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From: Sunshine Coast, Queensland, Australia

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A rumble?? only when coasting. Any idea from where this sound is coming from? right? left? Front or rear? Under your seat?

Aug 27, 2022 | 10:10 PM

How Are You

Drifting

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From: Brampton, Ontario Canada

Differential bushing or u-joints?

Aug 28, 2022 | 02:20 AM

clayzigler

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From: Missouri

Quote:

Originally Posted by MelWff

Is the sound coming from the back?
when is the last time you checked/changed differential fluid?

I recently bought the car. So far I had to replace the calipers, tires, and exhaust. I have not done anything with the differential fluid.

Aug 28, 2022 | 02:22 AM

clayzigler

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From: Missouri

I can only hear it when The windows are up. Not sure where the sound is but might be under the seat. I will have to try again. Also, can only hear it on the highway.

Aug 28, 2022 | 11:42 AM

barkingrats

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From: US-PNW

For those more familiar with gear mesh characteristics, could this be caused by excessive backlash from wear?

Aug 28, 2022 | 12:09 PM

MelWff

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Quote:

Originally Posted by 67:72

For those more familiar with gear mesh characteristics, could this be caused by excessive backlash from wear?

exactly, which is why I asked in an earlier post, is the noise coming from the back of the car.
A first step would be to drain and refill with a 85W140, not sure on first number.