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#1
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Help diagnosing belt driven squeal
I have been chasing down a belt driven squeal/metallic grinding sound. I have swapped out belts, and taken belts off to try and figure this out.
The engine runs smooth and quiet until I get the rpm's up to 2800 and then I get what sounds like a metallic grind or squeal. Has anyone had an alternator bearing issue, but not till you get to about 2800 rpm or higher? I ask about the alternator because it is the only thing I haven't replaced yet. Thoughts?
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1971 Trans Am - Sold 1977 Can Am - Sold 2002 Trans Am Firehawk - Sold 2004 GTO - Sold 2006 GTO - Sold 1970 GTO - Sold 1972 Trans Am - Sold 1970 Trans Am - Current Project |
#2
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No, or improper (Heavy-duty, Severe-duty) clutch fan? 2800 rpm causes the fan to drag so much the belt slips? 2800 rpm causes the flex-fan to touch the shroud?
HOW do you know that the sound is from something belt-driven, and not a vibration somewhere else? |
#3
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first i would try spraying belt dressing while revving the engine to see if the sound even changes. then i would put a stethoscope on the alternator.
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The Following User Says Thank You to i82much For This Useful Post: | ||
#4
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I just replaced the fan clutch, so I hope that is not the issue. I checked to make sure the fan is not touching the shroud, but I will double check it.
The noise is dependent on engine RPM, usually right around 2800 or higher. I will try the stethoscope method
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1971 Trans Am - Sold 1977 Can Am - Sold 2002 Trans Am Firehawk - Sold 2004 GTO - Sold 2006 GTO - Sold 1970 GTO - Sold 1972 Trans Am - Sold 1970 Trans Am - Current Project |
#5
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Are you 100% sure the sound is coming from the front of the motor?
If the car has a auto trans I have heard a cracked flexplate sound all too much like belt slippage.
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I do stuff for reasons. |
#6
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2 widths for belts. Make sure you have the correct width for the pulleys you're driving.
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72 Luxury Lemans nicely optioned |
The Following User Says Thank You to indymanjoe For This Useful Post: | ||
#7
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Run the car down the road with the alternator belt off. That should rule it out.
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1968 Firebird 400 RAII M21, 3.31 12 bolt, Mayfair Maize. 1977 Trans Am W72 400, TH350, 3.23 T Top Everyone you will ever meet knows something you don't. Bill Nye. |
#8
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I have the exact same problem — squeal starting around 3k rpm, and I too just replaced the fan clutch. I swapped out the standard duty for a heavy duty and did the mod to the bimetallic strip to start it sooner.
I roughed up the pulley grooves a smidge and I’m going to try slightly wider belts. Forgot how much fun it is shopping for v belts . . .
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1976 Trans Am Buccaneer Red 468ci, 10.5:1 CR, 87 CC RPM CNC e-heads, HR 282/288, 230/236, 561/.573 lift, Johnson Lifters & HS 1.65 Rockers |
#9
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Quote:
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#10
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Quote:
In any event, I don’t remember saying anything about wondering why it slips . . .
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1976 Trans Am Buccaneer Red 468ci, 10.5:1 CR, 87 CC RPM CNC e-heads, HR 282/288, 230/236, 561/.573 lift, Johnson Lifters & HS 1.65 Rockers |
#11
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The new belts fixed my squeal. The issue wasn’t the new clutch exceeding the OEM design, but the current slate of available v belts on the mark. Many of the belts that are listed as correct are actually sized metric, which ends up a bit narrower than the stock 7/16” width. Gates, which makes a good belt in general, says their 7000 series belts fit and lists them as 7/16” width. But they are actually 10mm, a bit narrower than 7/16.” Goodyear Belts came out with a new line of belts, and the width is almost exactly 7/16,” just a hair over. That’s what I’m trying now, and they seem good quality so far.
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1976 Trans Am Buccaneer Red 468ci, 10.5:1 CR, 87 CC RPM CNC e-heads, HR 282/288, 230/236, 561/.573 lift, Johnson Lifters & HS 1.65 Rockers |
#12
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Got a name for the new Goodyear belt line? Wouldn't mind filling that away for future reference.
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I'm World's Best Hyperbolist !! |
#13
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Quote:
https://goodyearbelts.com/
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1976 Trans Am Buccaneer Red 468ci, 10.5:1 CR, 87 CC RPM CNC e-heads, HR 282/288, 230/236, 561/.573 lift, Johnson Lifters & HS 1.65 Rockers |
The Following User Says Thank You to Brentco For This Useful Post: | ||
#14
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Thank you. Checked their site and they list a good selection for Pontiacs. And yep, just a few hundreds over 7/16.
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I'm World's Best Hyperbolist !! |
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