eroticryd

Mechanical question regarding my '96 Cobra conv., 80,000 miles.

I am hoping that one of you guys might have an idea as to what is wrong with my mustang - something that me and my mechanic have spent the past 2 weeks trying (unsuccessfully, of course) to figure out and correct.

Problem:
Following a cold start and after having traveled approx 2-3 miles, a "chirping" sound comes from under the car's rear end. Usually sounds like birds, and sometimes a little like crickets as well. The faster I go, the faster the chirping. It is perhaps not quite as loud as squealing brake pads, but still loud enough to hear w/ the windows up and radio on. Lasts for about 1-3 miles and then disappears. Will not reappear unless I let the car sit for a couple of hrs and then begin driving again. This sound only seems to occur only when the mustang is cold and within the first 2-3 miles of a trip.

Using the brakes does not alter the chirping except that the deceleration of the car causes the chirping to slow up.

Problem has existed for about 3 weeks. Could this be a non-mechanical issue…..maybe metal parts expanding/contracting and rubbing? Weird thing is that regardless of the what the temp has been recently (35 degrees or 60 degrees), the chirping always comes within 2-3 miles and lasts for about 1-3 miles of driving, whether at hwy speeds or slower city speeds. Even considered the possibility of a rubbing exhaust heat shield, but that does not seem to be the issue, either. Oh, and looked for a damned bird's nest back there too - - - and nada!

Here is what I have had done to the vehicle these past two weeks:
1) replaced ring gear bearings (left and right sides)
2) replaced universal joints (front and rear)

Here is what we have ruled out as being a potential problem:
1) rear brake parts (to include pads, rotors and calipers).
2) pinion and axle bearings

Any enlightenment as to what might be causing this problem would be much appreciated.

Thank you.

-Mark

MTShambles

Driveshaft squeaking maybe?

Thats the only thing that I can think of that would speed up and slow down.

eroticryd

Thanks for the reply and the suggestion that it could be the driveshaft. We did replace the ring gear bearings (spider gears) yesterday, so at least those are not the problem.

My mechanic said that there is a an extremely rare chance that something actually INSIDE the driveshaft might be wrong, which would require the replacement of the entire driveshaft. But he said that the possibility of this was so rare that he doesn't really hold much faith in that being the issue. But maybe it is not as rare as he thinks? I just want to get that darned thing quiet, again!

MTShambles

Well thats the only moving part that I can think of that would speed up and slow down with your RPM's. Check the yokes where it meets with your tranny and so forth.

Other than that, I have no clue.

eroticryd

Thanks again, Chris. I, too, have thought that it must be something to do with the driveshaft.

Did a couple more tests today (which means I left the radio off and listened for the problem more deligently). What i found was that on a completely cold start the chirping starts real slow and begins around the 2-3 mile range. Even at a constant speed (say 35 mph), the chirping gradually increases in frequency and, after a minute or so, begins to gradually decrease in frequency until it totally ceases and does not return during that entire trip (usually takes about 2-3 miles from onset to end). Speed does has an effect on the frequency of the chirping as well, with the faster that I am traveling causing more frequent chirping.

In addition, I found that the longer that my car is parked, the longer it takes for the chirping to begin once I start the car up and drive it - seems like any time frame over 2-3 hrs results in the chirping beginning around the 2-3 mile range. When parked 1.5 hrs, the chirping started within about 1.5 miles and when parked for an hour it started within about 1/2-2/3 mile. And the chirping seems to end more quickly during these "warmer" starts.

So to me is seems to be some type of lubrication issue with regarding metal parts(although I am definitely not an expert) whereby the lubricant must be sufficiently warmed up in order to cease the chirping made by some kind of metal parts. But, if this is the problem, then what is surprising to me is why the chirping doesn't start immediately when driven from a cold start? Why does it wait until the car is semi-warmed up before the chirping starts and then quits when the car is totally warmed up? And since we've already ruled out or replaced the right and left ring gear bearings, front and rear universal joints, rear brakes, and pinion and axle bearings.....then what metal parts, bearings or bushings might be causing this?

If you or anyone else has any more ideas or answers, I'd love to hear them.

czwalga00gt

Sorry for not reading all of your post... i'm a little frustrated from losing a game of nhl 2005 haha... but i kinda had the same problem right after i got the car... threw some new pads on and it was fine.

It was a consistant chirp/squeek and you could hear it worse when you were next to walls.

ackuric

If you knew what you were doing during the tests, you'd get the vehicle off all 4's (if you didnt have the means to do so, do one axle at a time, but since its your rear thats all you should need, and since its a rwd car, with the rear lifted up, you can attempt to 'run' the vehicle) and test it right there in person, no motion, and locate the sound directly, and BAM, spray 3 cans of lube, or replace the part =p. and if by chance you didnt get the same effect as you would when you drive the car cold for a few miles, i guess it would have to be suspension related!

it seems you've invested quite a bit of money to fix the problem, but have yet to even analyze the situation, correctly.

Sounds like your trusty mechanic is getting a pertty penny outta you.

eroticryd

Thanks for the suggestions, guys. Did run the car w/ the rear end up and wheels/brakes removed, and the squeaking did come and go (hence the reason we ruled out the brakes).

Going to take your suggestion, ackuric, and have a shop put the car up again and try to locate exactly where the noise is coming from.

Another friend of mine mentioned that I should also consider looking at the antilock sensor and pickup wheel assembly.

I hope to have the problem ID'd by next week and will let you know what it ended up being.

Again, thanks!

-mark