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I was driving my Camaro to the Pleasanton Good Guys show this morning and after about 30 miles it all of the sudden started making a wierd noise. I describe it as a slapping sound against the fiberglass hood, but it was not that. It sounded like one of the ribs from the 12 rib Procharger belt broke and was still on the motor but enough has ripped/broke to slap the underside of the hood and it rotates...... What I have do so far:

Pulled over looked at belts (V-belt and 12 rib), both checked out ok, I saw the overflow a little loose, so I zip tied it to the radiator mount to make sure it was not loose and rattling and hitting the frame.... Got back on the road, seemed ok, began increasing speed and once again sound came back, exited freeway turned into gas station again checked, can't find anything. Checked the underside of the hood not a mark on it..... Also checked blower boost lines to see if one loose and blowing something against engine compartment and all good. Start heading home and try to go down my own checklist. I checked while driving with a maglite through the cowl hood and could not see anything flying around under the hood.

Ruled out:

Motor problems - not RPM sensative
Procharger problems - not boost sensative

That's when I made the connection between the sound and the speed. @ 40 mph in anygear, at any boost level, the sound starts, below 40 its gone. Not fading away below 40, completely gone..... As MPH increases so does the rate of the sound. Once the sound was being made I hit the brakes both hard (not locking up) and pretending like I'm coming to stoplight and it does not stop the sound until I get before 40 mph. The car does not "jump" around or "shake" when sound is being made.... By the time I got home, my wife drove along side me after I got home and she thought it sounded like it was coming from the front end passenger side, (same place I thoiught)... Any ideas for me to check? I was thinking maybe wheel bearings? I don't know what else to check. Thanks....
 

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My '55 Chevy made a slapping sound above 40mph (passenger side) also and took a while to settle down - lower rpms. It was the heater core slapping inside the heater box. The high flow of coolant at higher rpms caused it to flutter inside the box. I had to let someone else drive my car, sit in the passenger seat at high rpms to figure it out. I hope your issue is that simple.
 

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I second the passenger approach. I have ridden as a passenger with my head in the footwell diagnosing sounds! Have you pulled the pass wheel to check for something flapping. Maybe it's flapping in tune with wheel rotation.
 

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Bad tire belt?

Swap front tires and see if the noise travels with the swap.
 

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Discussion Starter #6
Good ideas, I will try some of these out today, now all I need to do is find a pilot to drive it for me....

Swapping tires I can do, now that the heater was mentioned, it makes me wonder, I just finalized the Classic Air install and ran the lines to it the week before the show..... I wonder about the heater box/core...
 

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Re: weird noise @ 40 mph.... help please.

"weird noise @ 40 mph "

Hummm....I hear a weird noise when my wife starts screaming when I take off banging through the gears and gets real quiet when I get to about 95 mph :D

Kev
 
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