Odd Noise

[bike70ride]

Have this noise for a while now, and haven't been able to really figure out what it is. First off, it's basically non-existent when the temperature is below 40. Now that Spring is here, noticing it more.

When coming to a stop, when I get down to about 10 mph, I hear this odd "light clunking" noise...about 4-5 in succession. Can't really pinpoint where it's coming from other than the front of the car...sometimes it seems more on the passenger side, other times more in the middle.

I think it's transmission related, but not sure. Tranny shifts flawlessly, however. Car has ~27,500 miles.

The noise seems to be when the tranny is still in 2nd right before it drops into 1st. If I brake pretty lightly, the noise is almost non-existent, but if I brake harder and come to a more abrupt stop, it's much more noticeable. Other than a noise, however, there is no shudder, vibration or anything.

Any thoughts on what this might be? I do have the fairly common high speed (above 60) vibration...tires are quite new (brand new when I bought the car last year (22,500 miles)) and are wearing fine. Since this is low speed, maybe the 2 aren't' even related...

Thanks!

 

[jjcool00]

Always provide car details when posting, such as year, engine size, etc.

I had almost the same issue as yours, but from 3rd gear to 2nd and it was my PCM. It started light, but the longer I ignored it, the louder and louder it got. Although air temperature didn't change it at all.

Does it make the sound if you use the SST and shift from 2nd to 1st? That would be a way to conclude if it's the trans/PCM or not.

Edit: now that I re-read your post and you say 4-5 clunking noises in succession I can remove my thoughts about the trans/PCM. I would think it's something else that you can't hear that's still happening until the car slows down. A lot of noises get drowned out at higher speed but are still present. Maybe something up front is loose.

 

[LS4me]

........I do have the fairly common high speed (above 60) vibration...tires are quite new (brand new when I bought the car last year (22,500 miles)) and are wearing fine.......

What high speed vibration? I've had 4 LSes and the only vibration I have ever had was aftermarket wheel and tire flat-spot related.

 

[joegr]

What high speed vibration? I've had 4 LSes and the only vibration I have ever had was aftermarket wheel and tire flat-spot related.

A bad alignment or worn steering/suspension parts can cause the tires to wear in such a way as to cause vibration over a particular range of speed. A good while back, I had an issue like that with my 04 that took a little while to resolve.

 

[LS4me]

A bad alignment or worn steering/suspension parts can cause the tires to wear in such a way as to cause vibration over a particular range of speed. A good while back, I had an issue like that with my 04 that took a little while to resolve.

Forgot about that.... Bad shocks can cause a transient vibration.

 

[jjcool00]

A bad alignment or worn steering/suspension parts can cause the tires to wear in such a way as to cause vibration over a particular range of speed. A good while back, I had an issue like that with my 04 that took a little while to resolve.

Happened to me as well.... with worn shocks

 

[2002_lincolnLS]

when my rear tierods wore out my car started to vibrate horridly, new tierods and tires and now I can get up to 100 no vibration. My issue started around 70 and would get worse as you went faster so I rarely did until I replaced everything.

 

[bike70ride]

Always provide car details when posting, such as year, engine size, etc.

I had almost the same issue as yours, but from 3rd gear to 2nd and it was my PCM. It started light, but the longer I ignored it, the louder and louder it got. Although air temperature didn't change it at all.

Does it make the sound if you use the SST and shift from 2nd to 1st? That would be a way to conclude if it's the trans/PCM or not.

Edit: now that I re-read your post and you say 4-5 clunking noises in succession I can remove my thoughts about the trans/PCM. I would think it's something else that you can't hear that's still happening until the car slows down. A lot of noises get drowned out at higher speed but are still present. Maybe something up front is loose.

Forgot about the car specifics...was trying to describe the problem in as much detail as I could...

2006 so that defaults to the 2nd Gen V8 Sport...


Shortly after I got it, I had my local dealer go through it and they said it's in remarkably good condition and they didn't find any major issues. There was one bolt missing on the underside somewhere...I'd have to read the print to recall what/where as that was over a year ago now.

I know I read on here about a lot of people having high speed vibration issues associated with tire/rim combinations, alignment issues, etc. I mostly drive in the city so I don't get above 55 very often...and I have no issues with vibrations at city speeds. Since I had brand new tires when I got the car and the dealer re-balanced them when I had them do the "checkup" I thought that might cure the problem. It didn't, so I may try road force balancing...as I read that often solves the issue. I'm running the factory 5-spoke chrome rims.

The car is really quiet inside and I'm pretty attune to noises, so I think if there was something loose/worn in the suspension I'd hear it. The only thing I do know is that when I cross certain intersections with pavement ripples from cross traffic, that will sometimes cause a similar light clunking noise, but that is definitely coming from the rear of the car...I may have worn shocks in the rear or something... And that noise is more pronounced when it's cold (opposite of the other noise I'm troubleshooting!).

Thanks for the input so far...keep it coming if anyone has any more suggestions...

 

[bike70ride]

In reading some more old posts, I should mention my car doesn't have Advance Trak, as I see there was a TSB for a popping noise similar to what I'm hearing.

There is a TSB covering this issue........its nothing to be concerned about as far as I can tell. The only solution is to replace your ECM (electronic control brake module). My car does the same thing. Also, if you open your hood, you can see your ECM in the front right corner. Here is the TSB: http://www.lincolnvscadillac.com/showthread.php?t=7612&highlight=brake+popping