High pitch noise at 80mph?
12-05-2003, 09:53 AM
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High pitch noise at 80mph?
Anyone get this? I took a 3 hour trip a couple days ago and cruised at 80mph most of the time. After a couple seconds a high pitch type of noise was comming from the engine. If I gassed it or let off for a bit it would go away. Anyone get this?
Jason
Jason
12-05-2003, 10:05 AM
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I get a slight high pitch whining noise in 6th gear at around that speed. I think mine comes from the gearbox/transmission as opposed to the engine compartment. But, your noise goes away when you gas it? That sounds different as mine comes on when I gas it.
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12-07-2003, 08:08 AM
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I had the same problem: it would "whine" during cruise between 70-80 MPH. If you let off the throttle or get in it, then the noise would go away. It wasn't too loud that the radio couldn't drown it out. It seems to have diminished greatly at 8,000 miles.
There was a thread on this topic some time ago...
I know (with 99% certainty) that mine (with symptoms stated above) is good 'ol fashioned gear whine. You'll commonly hear it on heavy-duty trucks with high-ratio (numerically) gears in the rear end. It usually starts with ratios in the 4.xx:1 range, but I think the Z is a 3.78:1 or so. However, the rear differential housing in the Z is a lot closer to your head than in a pickup truck.
The core of the noise has to do with gear teeth meshing. The noise becomes audible when you have a lot of teeth (as with a high numeric gear ratio) rotating at a high RPM (70 or 80 MPH). The teeth can collide slighlty with another as they initially start to mesh. The ring gear (being a big, circular piece of steel) will resonate, just as a tuning fork will, when the frequency of the collisions matches it's own harmonic frequency. The resonant point (when you hear the noise) happens only under light loads because this is when the pinion gear can "bounce around" on the teeth of the ring gear and allow the ring gear to sustain oscillations (vibration). Under heavy load (accel or decel) the pinion's teeth are driven into the ring gear's teeth. This causes the ring gear to not resonate as freely. The situation is similar to beating on a piece of metal with a hammer: if you let the hammer bounce off the metal, the metal will ring. On the other hand, if the hammer hits the metal and stays "stuck" to the metal, it won't ring much, if at all.
Bottom line: if you measured the frequency of this whine, you would fine that it would equal the number of teeth on the ring gear times the revolutions per second that it rotates. (The "whine" frequency could also be a harmonic multiple of this number too.)
The only reason I'm 99% sure of this is that I reserve 1% for the manual transmission being the cause. I can tell from the gear noise (and the fact this transmission handles 270 ft*lbs) that it is quite beefy and probably uses straighter cut gears inside than most trannies. Nissan uses a "dual mass" flywheel in order to keep this thing quiet, in fact. However, except for 1st or 2nd gear, there shouldn't be anything rotating fast enough (or gears big enough) in the transmission to cause an audible whine...
There was a thread on this topic some time ago...
I know (with 99% certainty) that mine (with symptoms stated above) is good 'ol fashioned gear whine. You'll commonly hear it on heavy-duty trucks with high-ratio (numerically) gears in the rear end. It usually starts with ratios in the 4.xx:1 range, but I think the Z is a 3.78:1 or so. However, the rear differential housing in the Z is a lot closer to your head than in a pickup truck.
The core of the noise has to do with gear teeth meshing. The noise becomes audible when you have a lot of teeth (as with a high numeric gear ratio) rotating at a high RPM (70 or 80 MPH). The teeth can collide slighlty with another as they initially start to mesh. The ring gear (being a big, circular piece of steel) will resonate, just as a tuning fork will, when the frequency of the collisions matches it's own harmonic frequency. The resonant point (when you hear the noise) happens only under light loads because this is when the pinion gear can "bounce around" on the teeth of the ring gear and allow the ring gear to sustain oscillations (vibration). Under heavy load (accel or decel) the pinion's teeth are driven into the ring gear's teeth. This causes the ring gear to not resonate as freely. The situation is similar to beating on a piece of metal with a hammer: if you let the hammer bounce off the metal, the metal will ring. On the other hand, if the hammer hits the metal and stays "stuck" to the metal, it won't ring much, if at all.
Bottom line: if you measured the frequency of this whine, you would fine that it would equal the number of teeth on the ring gear times the revolutions per second that it rotates. (The "whine" frequency could also be a harmonic multiple of this number too.)
The only reason I'm 99% sure of this is that I reserve 1% for the manual transmission being the cause. I can tell from the gear noise (and the fact this transmission handles 270 ft*lbs) that it is quite beefy and probably uses straighter cut gears inside than most trannies. Nissan uses a "dual mass" flywheel in order to keep this thing quiet, in fact. However, except for 1st or 2nd gear, there shouldn't be anything rotating fast enough (or gears big enough) in the transmission to cause an audible whine...
Last edited by archman350z; 12-07-2003 at 08:14 AM.
12-08-2003, 02:52 PM
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I experienced this just once, precisely at 80 MPH. I was just about out of gas (DTE blinking, damn that thing) so I filled the tank & the noise went away. I think it was the fuel pump.
07-27-2004, 09:40 AM
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I have it too!! I notice it only in either 5th or 6th gears, going around 80mph... but it only happens when you press the gas peddle pressed enough to keep going the speed. When you give it more gas it goes away, and when you remove your foot it goes away... i hear it coming from the front right side of the engine compartment.. i thought my car was broken!
07-27-2004, 10:42 AM
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This thread is such a relief. Same here, ~80, 81 mph with even throttle position, no load on engine, just cruisiing in 6th on a flat road is when it's most noticeable. So glad to hear it's normal. I often wait for one of my passengers to bring it up, but they havent so far...