Slide-whistle-like sound in 3rd?

I have recently been driving with the radio off and paying more attention to the sounds the car makes. I've started to notice what I think is best described as a sound like a slide-whistle going from low to high pitch when I accelerate in 3rd between 2500-3200ish RPM. As far as I can tell, this sound is not there in either 1st or 2nd at any speed. Hypothetically speaking, if I were to accelerate hard past 4-4.5k RPM in 4th / 5th (can't say which for sure) I would hear the sound again. This noise is distinctly different from the normal engine whirring sound and appears only to make itself heard in a very narrow range of the RPM band and only in a couple of gears. What is this noise? Even though I have no problems shifting, I have a sickening feeling that it's probably transmission-related given its occurrence in only a couple of gears. Any thoughts?

have the same thing here but between 3k-4k in 3rd, only in winter when the car is cold. On real cold days it doesn't go away until i really push hard. It must be gearbox or transmission related since I experience it only in 3rd. noticed this since first winter - 2000 c4

Hmm... I can actually hear the noise up to around 4k rpm, but it's much more obvious around 2.5-3k. It doesn't go away even after driving around for an hour or so, but I don't usually push the car that hard. The noise may be temperature related in my case as well as I'm not sure this noise was there in the summer. However, I wouldn't say that the temps around here ever get 'really cold' -- it's been about 45-55 degrees the last few weeks.

guys, sounds to me like you have the same issue i have and am currently resolving. Mine was starting to make a noise that I only heard in 2nd and 3rd gears, b/w 2500-3500 rpms, then later, all gears and all rpms. diagnosis, shot differential/transaxle: Cost: roughly 3,000 bucks. OUCH. well, at least while the whole engine is out i am going to put a new clutch, rms, spark plugs, and bellows tube. ($3k for diff alone.) hope you guys dont have the same issue as me, but if you do it would be somewhat reassuring for me to know that I am not the only one with this problem (3 porsche specialists in los angeles said they havent seen a diff go bad yet) just my luck i guess. Thank god i have a wife that doesnt mind me spending money on my ride. P.S. rootkid, love the color (mine is the same 99 arena red/savannah beige, what is your interior color?) Peter

nsx4pete, Interesting... Were you hearing the same slide-whistle-like sound when accelerating? From what I recall reading of your issue you described it as more of a low rumble / rubbing sound? This definitely does not sound like that. I'm hoping it's not the gearbox (seems the most likely source if it's only in a couple of gears), but I suppose I'll have to take it in to find out for sure. I do find the possibility of a drivetrain failure in < 30k miles pretty irritating. I don't even push the thing that hard! Thanks for your comments about the color. It's actually Orient Red Metallic -- I believe it replaced Arena Red as a factory option on the 996es starting in 01. My interior is black, which I gather makes a pretty rare combination as the orient / arena cars usually seem to have beige or gray interiors. BTW, there is a 993tt in Arena Red that I see at work sometimes. The color on that car just looks amazing in the sun.

A followup: I brought the car to the local dealer the other day and took a tech for a ride. He thought it was probably the ring and pinion gearset and said it sounded like normal gear noise to him; nothing to worry about. It doesn't sound like there is an easy / cheap way to eliminate the noise (and maybe no guarantee that it will go away anyway), so I suppose I will just live with it until it really gets to me or something breaks. During the drive he also pointed out that the noise was there in all gears. I think he's right -- on the way home tonight I was playing around with the gears and it appears that the whine is there and is roadspeed related moreso than gear-related. I think it just happens that 3rd is perfect to hear it -- has enough torque to push the gears hard enough (amplifying the noise) while still being quiet enough to allow the whine to be heard above the engine sound. Thoughts?

root, Is your "whistle" temp related like mine? or is it allways there? Currently it is -3deg celsius (edit 26F) here and It is very good audible on my car but only in third. It is not "gear load" related, I hear it even when just rolling in gear between 3000-4000 As soon as days reach about 10deg (edit 50F), I don't here it anymore. I was worried at the beginning, the first winter... then in spring it vanished only to come back the next winter again. It's stable, not getting worse. Now 5 years later I simply live with it. 'nix rulez

I don't know if the noise is temperature related or not, because I haven't really been listening for anything until recently and the temps have been pretty consistently below 55 F or so the whole time. It may go away when it gets warmer, but I won't know that until the spring. My noise is load related. I don't hear it when i'm just coasting in gear around those RPMs, only when accelerating. I think that all I can do is just keep checking on it and wait until it either goes away or gets bad enough to warrant replacement.