Hi,

I just bought a 98 C5 about 3 weeks ago or so. I noticed a noise that's comming from the back whenever I am driving. It's almost as if the tires are rubing or something. but I checked the tires and there is no weird wear patterns. so it's not the tires. it's a noise that keeps repeating itself every two seconds and the faster i drive the faster it repeats itself, so it has to be something that spins and is propotional to the speed of the car. I am just not sure if the rear end would do that or if it's the tranny. I will take it to a mechanic soon, but I was hoping to get some advice before a mechanic gives me the run around. Thanks a lot in advance.

 

I'm not sure exactly what it sounds like, but the early cars had a rather noisy fuel pump that I believe is located under the kick-up behind the driver's seat. Good chance that's what it is. Or maybe a bearing.

 

On my 98 the fuel pump makes a whinning noise until the car warms up, but if you have the goodyear run-craps (flats) you will always here the tires turning. I just got used to the noise, it's a sports car, plus, I just turn up the stereo anyways...

 

thanks for the inputs guys, but It not really whinning, it's more like a rubbing sound that keeps pulsating, and the faster I travel the quicker it pulses. I almost thought that part or the tire is rubing but it's not. I wonder if that's the sound a bad rear end makes or something.???

 

Congrats on the car and welcome to the forum.

Have you crawled up under the car to take a look at anything?
Rock in a tire thread? Something wrapped around a half shaft?
Any fluid leak from the rear end?

Just throwing some ideas out there.

Hope its an easy fix.

 

good idea, i will do that tomorrow. could it do that from needing alignment?

 

I would not think the need for an alignment would cause a speed related noise like that. It would be a good idea to have the alignment checked though for general purposes.

Maybe someone else with some more ideas will chime in.

 

a broken belt in one of the tires? or the harmonic melody of the runcraps themselves on the pavement...

 

My '98 was making the same kind of noise, but from the left front. I was going to get it looked at, but then I sold the car and bought my '03.

Yours isn't a Torch Red with Oak interior by any chance?

 

Mine made a noise like that. It was a bent hub. Someone pulled out in front of me and I hit the median trying to avoid her. Could possibly be that.

 

I would check the air pressure in the tires . When the run flats are low they make some crazy noise. you could have a flat without knowing it

 

I'm a dumb female, but could it be a brake noise? I know that on my old 77 C3 the pads could rub against the rotors even when the brakes were not being applied. But maybe this can't happen in a C5?

 

Sounds more like a worn Wheel Bearing Hub Assembly Unit (a constant whine that increases with acceleration, and, decreases accordingly with de-acceleration, and/or, emanates from the affected corner when steering into a long sweeping turn). Moreover, these specific items are sold as "complete assemblies" which include the speed sensor attached to the hub, AND, are available for just under $150 each. Timken is the popular o.e. manufacturer for the wheel bearing hub assembly unit. And, the Timken bearing and hub assembly part number for the rear is #512513. Good luck to you.

 

It seems like the 3.15's make a little bit of a noise. Couldn't exactly describe this sound but it is kind of a spinning sound coming from the rear, especially in 3 over 50 mph. Do you have an A4 w/3.15 ? If so does it dye down when you shift to OD?

 

wow, thanks a lot guys for the suggestions. I knew i would get lots of inputs. I will explore each of these posibilities. it's an A4 with 3.15 I really hope that the problem is simple. I just wish i knew an honest mechanic that would Identify the problem without making it sound big.

 

Don't underestimate yourself.
My C5 did that when I first purchased it.
It turned out to be a warped rotor on the left rear.

This could be a possibility here too.

 

Try hooking up with some local folks in a club.
Maybe post your location and perhaps someone could help direct you.

Best of luck.

 

Don't you every let me catch you saying that again.

 

that's what my front noise was

 

I will be looking more into it this weekend, I will update you guys on what I find, i might take pics so that you guys can help me better too. Thanks a lot for everyone's help so far.