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Metal screeching sound while on freeway


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While cruising at 60 MPH, I started to hear some random metal screeching from the engine area that got louder and louder as time went on.  When a screech would happen,  could feel it on my feet and the engine would pull back a little  Sounds like it is in the #6 cylinder area or where the transmission connects.  Screech would last a fraction of a second.  Any ideas what this could be?

 

- I have a slight clunk near the rear when shifting.

- When accelerating to 6200 RPMs, near 4800 RPMs and up, it will metal screech slightly and I will feel flat spots.

- I can't get the screeching with the car revved to 6200 RPMS when not moving and in neutral

- Gears shift fine, oil pressure is good, and engine was 170 degrees the whole time.  No smoking after driving.

- Sounds similar to our old Nissan truck when you turn on the AC except my 280Z does not have heat or AC.

 

Any clue as to what I should look for?

 

 

 

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Clunk in the rear when shifting can be from a few things, most likely the front diff mount. Try driving in reverse and forward from a stop and see if the clunk is louder in one direction, that will help narrow down which mount. Alternatively it could be the half shaft joints, once under load they wouldn't make noise but when you get off load to shift the u-joints can clunk.

 

First thing I thought of is a loose belt. That would be similar to your truck as you state, probably a seized AC compressor or a glazed loose belt causes the belt to slip when the AC compressor kicks in. Your car I would say this would be most similar to a loose accessory belt. The faster the crank spins the faster the belt has to spin. What does your volt meter say as you drive, do the volts drop? That would very easily indicate a slipping belt. Have you checked the tension? Grab the belt and twist it, if you can get it 90* I think that is the industry standard for too loose.

 

Short of that it could be something like your engine rocking over and contacting something under load. Although that would not be screeching, more of a scraping noise.

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