Can't figure out groaning noise

[kmartind]

For some time now I've been hearing a groaning noise, but only after a hard run. It changes with vehicle speed (not engine speed) and does not change much when applying or releasing the brakes, or engaging/disengaging the clutch. Hard to describe, but it sounds most like a groan that becomes lower in pitch as I slow down. So far, no luck pinpointing the source. It's definately not a clicking or rubbing or squeaking sound which would be much easier to diagnose. At higher speeds it sounds slightly more metallic and much higher pitched, reminicent of a hard disk drive with a failing bearing or a screwed-up turbo.
The funny thing is if I drive like a grandma, the noise never starts, but once I hit it hard, even through 2nd gear it comes on noticably loud. That makes me think it might happen when "something" heats up, whether that something is a differential, transfer case, tranny, a bearing, or something else, I can't say with any certainty. I recently put Pennzoil Synchromesh in the tranny (just because it needed it, not as an attempt to fix this problem), and that had no effect.
Anyone heard a similar noise and ever figure out what it was?

 

[Lordpaxin]

Wheel bearing?
Axle
Drive shaft carriers

something that would get some flex when you mash it.

 

[Defiant]

Originally posted by kmartind
For some time now I've been hearing a groaning noise, but only after a hard run. It changes with vehicle speed (not engine speed) and does not change much when applying or releasing the brakes, or engaging/disengaging the clutch. Hard to describe, but it sounds most like a groan that becomes lower in pitch as I slow down.

When I get that, it means I forgot mom was in the car.

 

[kmartind]

Yeah, that might be it...
Although, I think that's typically more of a whining, nagging noise

Anyway, I'd like to pinpoint the source without having to go blindly replace parts because they "might" be it, but since I can't seem to get it to happen in the garage that's harder than it looks.

 

[leet]

My car was making that noise for 1 day before the intermediate shaft bearing failed. Catastrophically. Do you hear any grinding crunchy noises too?

 

[kmartind]

No grinding or crunching or scraping noises so far, just the groan/whine (depending on vehicle speed), and usually only after I've hit the gas hard at least once. It's not really loud, I'm the only one who seems to notice it and it's been going on for quite some time without really getting any better or worse. One solution is just to turn on the stereo but that only works until something important fails, possibly causing further damage.

 

[Lordpaxin]

Well, put it up on jacks

and drive it
get it up to speed where it makes the noise, then go around and listen for the sound.

or get a piece of pvc pipe and listen through it to pinpoint the noise.

 

[iwin]

It MIGHT be you rear differential.

 

[krazyMitsu99]

I have the same problem with my car (99mitsu eclipse). I sounds like its coming form the back, when I accelerate from a stanstill or low speed. It vanishes when I settle into a steady speed. Its like some sort ot "resonance" is happening and some loose mettalic parts are vibrating in sync.

Please let me know if you have figured out what was wrong with your car.

By the way, I had replaced the muffler a few months back. Also have a short-ram intake system and front and rear strut bars.

 

[kmartind]

Not really, but when I thought about it I think it's been basically doing this since almost new, it's only really noticable when it's a bit cold out and then I heat it up with a good run (after a normal warm-up of course). I think I may just be too paranoid, but I'll check out more possibilities as time permits and when I get things apart. I don't drive it that much these days as I'm working on more upgrades and it needs a clutch (which will be a good opportunity to check out the tranny, transfer case, diffs, VC, etc).

It sounds like you may have a different problem though. If you recently did the muffler I'd check the exhaust before getting too concerned, something could just be a bit loose or rubbing. Can you make it happen when sitting still by revving slowly (or quickly for that matter)? If you're N/T FWD, then several of the parts I suspect don't apply to your car. Could still be a wheel bearing or brakes but exhaust would be my first guess.

 

[krazyMitsu99]

I plan to have the exhaust looked at. i do believe the noise started a few months after I put in the new exhaust. And since the car had not been doing it befoer that, I guess the problem is different from your.

 

[gsxtacy]

I didn't notice your mileage......but the symptoms you described sound like low fluid in either the tranfer case or rear differential. U-joints also make noises like that when they get dry/worn.

Hope you figure it out.

gsxtacy

 

[krazyMitsu99]

My eclipse has 70K miles now. Its been making the noise for the last 2K miles. I did do the 60K service at around 65K and changed the timing belt and water pump at 69K, and the dealer didn't notice anything wrong. I will get it looked into.

 

[krazyMitsu99]

Took it to carx today. The guy said its the muffler just "cackling" . Supposedly the free flowing exhausts like the one I have start doing that after a while and it gets progressively louder. He said theres no fix except to replace the muffler. probably will get a second opinion.