C4 AWD Growl/Whine...

I bought a 2000 996 c4 cab, my first of the kind, :crying last year. I am noticing that the AWD system seems to be making a lot of noise. ie whine similar to a supercharger and it gets louder at operating temps. Here's the $60,000 question. Is this something I can "look into" myself or do I need to spend $1,000,000.00 at my local dealer? Like can I open the box under the trunck and poke around, are there fluid levels I should be checking, etc.? Any help would be appriciated.

Is the noise coming from the front or the back? One gear or all of them? Does it vary with RPM's or is it constant? Do you just hear it when there is wheel slippage or all of the time? Jeff '99 C4

Sorry for the lack of info. Here it is: It's from the front center, any speed, any gear and even in neutral coasting. It seems definitely to be an awd thing. It increases in ?pitch? with an increase in speed and vise versa. You hear it all the time not when there is wheel slip. Interestingly, it is much more noticible after driving a while (up to temp). I wonder if there is a fluid problem? There is nothing on my garage floor as far as leaks. The car as 45K on it. Well maintained. If you've ever owned a real 4x4 truck and had a front diff. go or had the pinion gears go bad it sort of sounds similar. I am trying to see if I can avoid the dealer trip. It is in storage for the winter now so it might be a good time to poke around. Thoughts?

soudns like a wheel bearing. im gonna go with left front

Really?? I've blown bearings before and got more of a "wobble wobble" sound. Plus it just came out of the dealer for the 45k service and new Pilots all around and a NYS safety inspection. That would be great though. I'll put it on jacks and tug at the wheel to check. Any reason you pick the left front over the right?

well chances are you wont feel it in the tug and pull method. Usually only with the car on a lift and the car runnign in gear you can hear it with a screw driver. Really if you have acces to a lift run it in the air and use a screw driver or pry bar to listen to each part to isolate the noise

and i picked left front becasue bad bearigns are always the left front on c4's or turbos and right rear on c2s and boxtsters, I have change a few left rears and one right front but LOTs more left fronts

Thanks, I'll try to check it out. I appriciate your help and input!

I was also thinking wheel bearings.....or it could also be bad tire noise. Do you hear it on the curves when you have the wheels turned a little while running? If the sound goes away when going thru' curves, then it's probably tire noise.

Did you find out what it was?

how do u guys even begin to know if it's a "problem"? i have a c4s and i hear the same tranny/drivetrain whining... it's all good.

eeek... I don't know dude. I had an 01 C4 and now my C4S cab and I've never heard anything like that.

I've just been driving through it. It's annoying and sort of loud though. I can't imagine Porsche designed it this way.

01 C4 here and no nice from my car either. I'm assuming this isn't just tire/road noise, right? I'd check the differential fluid levels as well as the transmission fluid level. Shawn

so you're teling me windows up, top up , music off coasting at freeway speeds u hear 0 drivetrain whine?

I'm experiencing a similar noice from my MY03 996TT. I have had a 996 C2 and now a 996TT (MY03) so I have nothing to compare it to as 2WD vs 4WD. The road noise was certainly not as perceptable on the C2 but that is about as near to a comparison as I can get. Is it easy to check the diff/tranny oil level? Cheers

It must be low enough for me to never have noticed, I'm generally sensative to noise like that - especially anything over 4kHz drives me nuts, but I will listen for it tonight.

i just changed my diff/tranny oil and the noise is the same. it's the same kind of whine u hear on those road cars that race... with those dog shift gears or whatever and it's that high pitched whine except magnitudes quieter per street car. i always thought this was normal and my car runs tight. maybe it is tire noise as i am running ps2s with 315s in the rear? i doubt it. it sounds mechanical and cool.

Cheers Riad

OK, listened real carefully with the top up and the radio off. I do hear the whine but I have to be honest I had to REALLY listen for it and as soon as I hit around 40MPH the road noise drowned out the sound. So the only time I heard it was when driving slowly and it was very faint.

I don't hear one either. Tire noise drowns everything else out. Brad, wouldn't you feel cooler using a stethoscope rather than a screwdriver to listen for noise?

Cheers Riad / Dresler

Funny topic. I have a 99 C2 and have exactly the same kind of noise. It comes from the middle/rear of the car and as stated above it sounds very similar to a supercharger. Just a very mechanical, high pitched noise that increases pitch with increased speed. I haven't noticed it get louder at operating temps though, mostly noticed when starting cold from a dead stop. I always just assumed it was normal drivetrain noise, coupled with less sound-deadening material in the early cars. Plus since it's sounded exactly the same for the last 40,000 miles I'm not that concerned about it. In that time I've replaced tires (which get really loud when worn), clutch, pressure plate, rear intermediate seal all with no difference.

I get a gear whine on my 99 C4. I think it is mostly due to how the gears are cut. I asked a few mechanics and even a drag racer I know. None of seem to be worried about it even after hearing the whine.

no not really the stehescope works the same but you lose alot of the feeling and sometimes you need the feel of a noise to find it.I bought these really cool electronic stetescope deal. The only thing its good for is listening to people talk across the shop,

I had the same kind of sound. I thought it sounded like a bad wheel bearing, since I had had the same sound on my Jeep and that was a wheel bearing. I took it in and they replaced a bunch of bearings on the serpentine belt pulleys under warranty. The service manager explained how they use some sort of listening device to isolate which bearings. Unfortunately they didn't get them all because I still hear some noise. I am going to have to go back and give them another go at it before my warranty is up.

Brad, I attended a local PCA Tech sessionat HBL on Sunday and a guy with a Boxster had the same complaint. He said he had 55 track days on the car. He didn't know if the nearly worn out slicks were causing the noise or a wheel bearing. I have had wheel bearings go bad before on my previous 911 and the tug method always worked. I have also had Pirellis that roared loud enough to drown the radio out. The wheel bearings seemed tight and I would not have guessed that the bearing would have been bad. HBL had a tech on duty so he put it on the lift and had the owner put it in 2nd gear under power. You could immediately hear the bad bearing at about a foot away. Good call.

I have a 99 C4 Cab, and I have NO whine....

No cheese either??

+1, its Tranny Noise... some of my friends think i have a Supercharger... Its just Drive Train Noise...

I can say I have a C4 and even on the Autobahn above 160MPH I have no drive train noise. Now wind, exhaust and tire noise is a different subject. Oh by the way what I am saying is from 0 to 170MPH and any speed in-between no drive train noise.

i think we need to actually be in the car to put a baseline on this noise thing... what one calls a whine may not be to others because their hearing ain't good, they're not in the right driving situation, road etc.

I feel pretty confident in the no drive train noise as I have an annual flight physical and can hear and feel noises and vibrations that are not normal in any aircraft I am qualified to fly and any car I have ever driven for any length of time. Realize strange noises or vibrations are a very very bad thing at 35000 feet and I think most Commercial/ ATP qualified pilots would say the same (ie you learn the difference between hydraulics on your landing gear, P3 Air big and little to the whine of a UHF/ VHF/ FM radio that tells you that it is working and you are on the correct frequency). Of course I have heard the strange noises not associated to an aircraft 3 times in my life which ended up with between 1-4 holes in my plane and 18 in my helicopter when I used to fly one back in the First Gulf War. Did not make me to happy but all 3 people who shot at me failed to live very long, one thanks to the USAF F-15, one to the Navy F-18, and the third guy was tracked by a UAV and received a Hellfire missile complaints of an AH-64, thanks guys!