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Hey guys, I have a 1978 Corvette that has been making a high pitched repetitive squeaking noise when driving at higher speeds. It only seems to happen when the car is warmed up, and driving at speeds above 45mph. The faster I go the louder it gets.
While sitting in the driver's seat is sounds like it coming from directly in front of me, and it is louder from within the vehicle than if I listen to the noise outside. I have played with gears and rpm, and it seems unrelated. Additionally, applying the brakes doesn't seem to affect the sound either. The only thing that affects the sound is speed.
I've attached a sound clip of the sound recorded from the inside of the car at about 55mph.
Any ideas? A bad bearing doesn't sound this high pitched does it? It's also weird to me that it is only occurring on long duration trips. I can go 60mph 5 minutes into the drive and it doesn't make a sound.
From: Loud, Raw and Dangerous 1968 327 4S in Southern California
If it doesn't change pitch with changes in rpm's it would seem not to be engine/alternator related. Have you tried changing the speed of or disconnecting the ventilation fan?
If it was engine related, it would be RPM dependent.
Does the frequency change if you change speed? Does it stay the same if you pop the car out of gear and coast? If so, I'd suspect a wheel bearing, or something scraping on a wheel/rotor.
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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Having listened it I'd be tempted to say that it might be something to do with the speedo cable? You say it sounds as though its right in front of you when you are driving. Could be the cable, or maybe the speedo head itself, it just needs to "warm up" a bit to squeak?
To reiterate, if you shift into neutral at speed, the sound stays the same? I think it's a rubbing squeak rather than a rotational bearing squeak (which should change with engine speed). Have you noticed any difference due to road smoothness?
I'd suggest it's an exhaust connection pipe squeak -- check the connections at the manifold and the frame's transmission crossover.
Yes, the sound remains the same when shifting into neutral at speed. I don't notice a road smoothness difference either. Super confusing to me. Ill check connections at manifold/transmission crossover.
The heat seems to be a big factor in the noise. As soon as I start to feel the hot air coming from floor/vents after driving for a while, the sound begins. Then that sound is completely dependent on the speed I'm going.... not the engine, gearing, brakes, or turning!
Last edited by ahugo75; Mar 16, 2024 at 02:29 PM.
Reason: forgot to mention
I,m unclear. Is the noise only while car is moving? If so, it sounds a lot like the speedo head to me. I had this happen once, but the speedo needle bounced around at the same time as the noise. Good luck.
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2024 C3 of the Year Finalist - Unmodified
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Originally Posted by beachmusic
I,m unclear. Is the noise only while car is moving? If so, it sounds a lot like the speedo head to me. I had this happen once, but the speedo needle bounced around at the same time as the noise. Good luck.
Agree. I'd said maybe the cable, but listening to the recording a few times (and comparing it to how our '78 sounds, it does sound like it could be the speedo head. The OP says that he hears it as soon as warm air is coming through the vents. If that warmth was enough to allow the cable to flex a little maybe that would squeak, or maybe warm the actual speedo head, with the same results.
If it was me I'd pop the speedo cable off the head and go for a drive before doing any major disassembly of components.
The speedometer was the issue; I disconnected the cable from the head, and the noise was eliminated. Thanks for all of the ideas guys! It's interesting that the cable would warm up and then start squeaking.
Now it's a question of how to fix this problem. The cable was working; just noisy... Should I pull it through the housing and grease it up? Then try to funnel it back through?
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2024 C3 of the Year Finalist - Unmodified
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Glad you got the noise isolated - I thought it sounded like the speedo when I listened to your recording.
When I changed the speedo cable on ours (to re-instate the cruise control) I released it from the speedo head and tied a piece of string to the end. I then pulled the cable out from the engine bay, making sure I had enough string left inside the car. I then swapped the old cable for the new on the end of the string and gently pulled teh cable back into the car. A little tricky, but it worked and it meant the new cable followed the same route back to the speedo head. Of course, you still have the fun job of fitting it at the gearbox.....😱
On balance, I think if you can, I might try pulling the inner and greasing it, and feeding it back in!😄
The only caveat to all the above that might be that as the noise stopped when you dis-connected the cable from the speedo head, does that not imply the head is the issue? Just a thought.....😳
Hey guys, I have a 1978 Corvette that has been making a high pitched repetitive squeaking noise when driving at higher speeds. It only seems to happen when the car is warmed up, and driving at speeds above 45mph. The faster I go the louder it gets.
While sitting in the driver's seat is sounds like it coming from directly in front of me, and it is louder from within the vehicle than if I listen to the noise outside. I have played with gears and rpm, and it seems unrelated. Additionally, applying the brakes doesn't seem to affect the sound either. The only thing that affects the sound is speed.
I've attached a sound clip of the sound recorded from the inside of the car at about 55mph.
Any ideas? A bad bearing doesn't sound this high pitched does it? It's also weird to me that it is only occurring on long duration trips. I can go 60mph 5 minutes into the drive and it doesn't make a sound.
hello, i had a similar noise issue on my '89. mine turned out to be the smog pump AIR injection pipe coming off the cat. not sure if your car has the same smog setup.
Weird Noise. Need advice/help diagnosing!
