Hi everyone, need some help here....

I recently aquired an '05 AT coupe, and above around 50mph, I start to get a very slow, rythmic vibration that can pretty much only be felt in the peddles or floorboard. It has a sound to go along with it, and I can't tell where it's coming from.

The vibration/noise is so slight that most people who don't suffer from massive used car buying paranoia wouldn't notice it. I only noticed it after I got it home for a few days, but now that I've heard it...

The best way for me to describe the "pattern" of the sound is this: Think of traveling at 70mph on a road that alternates from very smooth to slightly rough, and it swaps from smooth to rough around every 150ft....back and forth. I haven't tried putting the car in neutral yet to see if it still does it.

If I missed something about this, or it's in the wrong area, my apologies. Not sure what's causing the noise, so I wasn't quite sure where to post it. I did try searching. Any help would be greatly appreciated.

Update:

I've had the car for around 3 weeks now, and I've been looking for a replacement air filter for the Stillen intake the car already had on it. The filter was in very bad need of replacing. Work and laziness finally subsided enough for me to find the size filter I needed, and it was delivered yesterday (K&N, since I knew what the part number was from another post here).

Anyway, after finally getting it installed, I took it out for a spin to make sure I'd put everything back together right. I wasn't listing for anything in particular, but once I reached highway speeds, I immediately noticed the sound and subtle vibration this thread was originally about was now gone.

I'll leave it to the experts to tell me what happened. I wouldn't have thought a dirty air filter could have done that (was the engine being choked down?), but I changed absolutely nothing else on the car, and drove on the same road I always do. Regardless, the problem appears to be solved.

 

check tirewear

 

Thanks, but it's not the tires. I now know that it changes tone when I shift into neutral. Same pattern to the sound, and it almost seems like the engine is the culprit. Like it's changing RPM speed, but not going faster or slower as the sound changes - just the slight vibration you can feel in the gas pedal, and the noise you can hear.

 

I have the exact same problem on my 05 AT. But, its seem to happens everytime that I didn't warm up the car long enough. Its more like a "BOOM" sound coming from under the car. My guess is there are air bubbles in the cooling system. Im going to bleed the cooling system this thursday. Ill let you know.

 

Pretty sure this isn't the same thing as mine. My issue happens hot or cold, and is very subtle. Certainly no "booms" to speak of.

 

With hard to find vibrations one measures the frequency and intensity at a fixed speed/engine rpm and uses mathematics to correlate rotational diameter with vibration intensity.
"Most automobile vibrations are caused by rotating components that are out-of-balance or out-of-round. Since the engine must be running for these components to begin rotating, the engine's crankshaft will be the point of reference for vibration diagnosis. Every rotating component will have a rotational velocity that is faster, slower, or the same as the engine's crankshaft. Determining the rotational velocity of each component in relation to the engine's crankshaft is the key to an accurate vibration diagnosis."



For example a 26" tire with 1 bad spot [radial force stiffness] creates a 13 Hertz vibration at 60 mph.
http://www.vibratesoftware.com/html_...iagnostics.htm
http://www.vibrationschool.com/

 

Thanks, but any ideas on what would explain the pattern to the vibration? It's not constant like any other vibration I've had/dealt with. This one comes and goes every 100-150ft as you go down the road. Not random at all, but very set in it's pattern. One moment there's a slight vib/noise, the next moment it's smooth sailing. Kind of like an old police siren.

If you have the radio on, and aren't listening for it or expecting to feel it in the floor board, you'd never know it was there.

 

It's your tires and/or wheel balance. Have your tread and balance inspected/corrected.

 

^ I'm going to take it in next week. Hopefully, it's that simple.

 

I think I have the same problem. I haven't rotated my front tires in like 20,000 miles.

 

i had the same problem, Its so light you wouldnt notice it unless you were looking for it.


I actually felt the vibration threw the Shift **** too.

Switched out my tires, and it went away.

This happened every time i went over 60mph

 

I balance my tires every 3,750 miles when I change oil. Every time my tires are out of specification.
Even 5 grams of imbalance is very feelable to those sensitive.
After buying 14 sets of tires on my [322,000 mile] 1990 Q45 I learned 10 years ago to only buy Michelin. I have records [before/after] of evey tire rebalance going back to 1992. Every offbrand but top of line Dunlop, Firestone, Bridgestone, Yokohama, Goodyear where horrible after just 8,000 miles.

 

I'd say check tire pressure. If not tire pressure your wheels are def. out of balance.

 

You couldn't have summed this problem up any better. I too also have a 2005 5AT and have the same problem. It's really annoying the hell out of me and it's keeping me from fully enjoying my new G. I have a long stretch of road that was just redone on my way to work and it's so smooth that it makes it more noticable. I actually look forward to rougher roads so I don't have to feel this repeatative vibration. I have gotten new tires (Bridgestone Potenza Pole Position), alignment, and three tire/wheel balances and I still have this vibraton Do you still have the same problem or have you fixed this?

 

I've been too busy to have it looked at yet. I've found myself taking the back roads these days just so I don't have to listen to/feel it. Of course, nothing wrong with taking the G through some winding back roads. I just wish it was simply because I wanted to.

As soon as I can get away, I'm taking it in and going to try my best to ride with them and show them what's happening with it. Very, very annoying, and like you said - it keeps you from fully enjoying this bad *** car.