: Clunking noise coming from beneath truck



V-Eight
05-18-09, 11:48 PM
I've never had any problems with my truck, but recently a clunking noise is coming from underneath somewhere along the exhaust system. Sometimes it will make a loud noise like something has fallen off, but nothing does. Other times there will just be a little bit of rattle. The engine still sounds strong, so does anyone have any idea as to what this could be? The truck is a 94 Silverado.

dirt_cheap_fleetwood
05-19-09, 11:33 AM
When does the sound happen? If it is when getting on the gas or just letting off 99% of the time is is U joints. It could also be the rear end. How many miles are on it?

V-Eight
05-19-09, 03:47 PM
57 000 km, so like 35ish miles? Just randomly, sometimes when accelerating but sometimes when just cruising. When cruising its usually just a slight rattle, but sometimes its a gut wrenching crunching noise. One time I had the crunch when I started the truck, which would kinda make sense because hot air is suddenly rushing through....

Krashed989
05-19-09, 05:53 PM
Maybe a heat shield on the muffler rotted off on one side. Could be a lot of things.

V-Eight
05-19-09, 08:15 PM
Happens mainly when turning and when on/off gas I've found driving today

Kev
05-19-09, 10:10 PM
Tie yourself to the undercarriage, have a buddy drive it so you can observe first hand, just be sure to ask him to avoid dips and speed bumps if at all possible.

dirt_cheap_fleetwood
05-19-09, 10:30 PM
Go under there and start yanking on stuff. If something is loose that is probably the problem.

Night Wolf
05-19-09, 10:36 PM
A damaged cat will cause a rattling sound, had that happen on my '93 Coupe. You can go under it and hit it with a wrench or something and see if you hear anything inside.

Otherwise I'd say a heatsheild somewhere along the line on the exhaust system. Had this happen on the Lincoln, but it would not be a loud clunking sound, instead it sound like pinging under acceleration.

Kev
05-19-09, 10:40 PM
A damaged cat will cause a rattling sound, had that happen on my '93 Coupe. You can go under it and hit it with a wrench or something and see if you hear anything inside.Yeah, sometimes they get wrapped around the drive shaft but I don't think you need to hit it with a wrench, I'm sure it's dead by now...... darn cats! :kitty:

Night Wolf
05-19-09, 10:55 PM
Yeah, sometimes they get wrapped around the drive shaft but I don't think you need to hit it with a wrench, I'm sure it's dead by now...... darn cats! :kitty:

Well, at least it's not a mattress...

http://memimage.cardomain.com/ride_images/3/2823/221/32055110077_large.jpg

http://repairpal.com/images/managed/content_images/blog%20images/runovermattress.jpg

Kev
05-19-09, 10:59 PM
Hey, those guys are all related aren't they? I can see it in their eyes .... :rolleyes:

V-Eight
05-19-09, 11:24 PM
A damaged cat will cause a rattling sound, had that happen on my '93 Coupe. You can go under it and hit it with a wrench or something and see if you hear anything inside.

Otherwise I'd say a heatsheild somewhere along the line on the exhaust system. Had this happen on the Lincoln, but it would not be a loud clunking sound, instead it sound like pinging under acceleration.

Yeah, its generally a pinging with the odd crunch. The first time it happened it scared the shit out of me lol. I was like "Oh ****! What the hell just happened?" What does the heatshield look like?

Kev
05-20-09, 12:11 AM
The heat shield is a piece of sheet metal formed to the shape of the catalytic converter, spot or tack welded to the converter with about a quarter of an inch gap to keep weeds or other loose flammables away from the heat of the converter.

If one or more of the welds have broken, which is common after time with the expansion and contraction, you should be able to tell by tugging at the perimeter until you find the loose weld. If that is the problem a good muffler shop should be able to tack it back on.

Kev
05-20-09, 12:13 AM
... and you thought I was just all fun and jokes .... :histeric:

V-Eight
05-20-09, 12:16 AM
Yeah, that is possible. It did sit in a driveway for a few winters before we got it. (From the same relative we got our SDV from, although the deVille was always garaged)

C&C
05-20-09, 06:03 AM
A clunking noise when either accellerating or decellerating can be an indication of bad univeral joints; something to consider.

V-Eight
05-20-09, 07:47 AM
How would I be able tell by looking at it?

dirt_cheap_fleetwood
05-20-09, 12:09 PM
Look for where the grease may have leaked out. Any black marks on the U joints are probably old grease. Take the two sections of the drive shaft that the U joints connect and twist them. There should be NO movement in them and they should make no noises at all.

V-Eight
05-20-09, 12:53 PM
There is a fair bit of black that looks wet on the front connector.....

C&C
05-20-09, 03:29 PM
You can sometimes hear the clunk by just shifting into gear; that is a pretty good indication of a bad "U" joint.

V-Eight
05-20-09, 04:40 PM
Listening to it again while driving it sounds too "tinny", like too high pitched to be the U.

V-Eight
05-20-09, 05:27 PM
http://www.youtube.com/watch?v=3sdfAnDQZDE

Here's a video, not the greatest, but you can kinda hear it around :23

orconn
05-20-09, 05:34 PM
Seems to me that 35k miles is rather premature for universal joint failure. But then I had a Volks Scirocco that required universal joint replacement every 11k miles during the time I owned the car.

V-Eight
05-20-09, 05:56 PM
But that's a Volkswagen for ya

dirt_cheap_fleetwood
05-21-09, 12:10 PM
I hear no sound on the video. Silent movies suck.

V-Eight
05-21-09, 12:33 PM
http://www.youtube.com/watch?v=2jCMENcuA98&feature=related

That one should work. To bad I didn't get a video while driving today, it was pinging like a mofo.

V-Eight
05-21-09, 01:49 PM
I tried to get one of the pinging today but you can't hear it in the video. Seems to happen mainly when going heavy on the gas.

dirt_cheap_fleetwood
05-21-09, 02:41 PM
The pinging could be exhaust, like the sound metal makes when it expands and contracts. It may be louder now because something is loose somewhere so something is sliding against something else because it has fatigued and the tolerances have become sloppy (worst sentence ever). I still think the clunking is U joints. Mileage is not always what determines wear. You have to remember, this is a 16 year old truck, things go bad. The rubber seals on the U joints probably dry rotted and the grease came out.

V-Eight
05-21-09, 03:34 PM
Yeah, I think its something loose in the exhaust because at times it will sound like something is bouncing around sometimes it happens on a shift. The clunking really sounds like a louder version of the pinging though. Could bad U joints result in a lag when you shift into gear? Yeah, I wouldn't be surprised if the rubber rotted. One of the old tires had a split down it from sitting all that time.

V-Eight
05-27-09, 07:52 PM
Problem was cracked manifold bolts and seals so there was a bit of shit in the exhaust and some shaking. The truck is so much more quiet now too....

93eldodave
05-29-09, 10:27 PM
If you have a seized up u/joint it will pop ,creak , sound like a rattle ,and also sound like a pebble rolling aroung in the drive shaft ...And it will also squeek when hitting dips or bumps...