Metallic chattering sound - Mazda B2500 (Ford Ranger)

Got a problem with my 1999 Mazda B2500 (Ford Ranger under the hood), and before I take it to my "plug it into the computer, no error codes, nothing's
wrong with it" mechanic, I wanted to run it by some people that know a little more about vehicles. Here's the basics of my truck & the problem
1999 Mazda B2500 4-cylinder engine 5-speed manual transmission 130,000 miles +/-, original everything (including clutch) 2-wheel / rear wheel drive
Problem: vehicle makes a metallic chattering sound (like someone with steel dentures chattering their teeth in the cold, best way I can describe it, or maybe like a dime rattling around in an empty beer can) intermittently. Sound seems to be coming from under the floor boards, close to the back end of the vehicle. Sound is worst when there is a load on the engine, especially in higher gears & when going up hill, or if I let the clutch out too slow when up shifting to a higher gear. Sound only happened once when there was no load on the engine. Engine sounds are normal, engine idles within normal parameters (500-750rpms), accelerates well both on flats and up hill. No idiot lights have come up on my panels (and this truck is like a nervous child, if it thinks even the slightest thing MAY be wrong, my dash lights up like a Christmas tree). Sound happens more often at lower RPMs (just before I down shift) or when accelerating suddenly.
I had chalked it up to an old vehicle with a loose panel or something else that's pointless to worry about, until today when a friend (and former mechanic) said it may be something in the driveshaft and/or rear differential. At first I thought the worst this could be was that my 130,000 mile clutch is finally giving out on me, even though it feels ok. When he mentioned this, I had nightmare images of a bearing seizing up and my transmission blowing out as a result.
Obviously to diagnose a problem, it helps to be IN the vehicle, but anybody want to shed some light on the above? Feel free to ask for more info. I'm just trying to get some feedback & suggestions before I take Chicken Little's advice about the sky (and my driveshaft) falling.
C.
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It sounds to me like a loose tailpipe hanger or muffler.
I would just have your mechanic check this things and check the fluid levels in the rear diff and the bearings at the next service.
Jeff
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From your description, it sounds like a loose or damaged exhaust heat shield.
On 4/4/07 5:39 PM, in article Pridnd5h_L-ctInbnZ2dnUVZ snipped-for-privacy@comcast.com,

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Ah, I forgot that. Very possible indeed.
A thorough underbody inspection may be of some value.
"E Meyer" wrote: > From your description, it sounds like a loose or damaged > exhaust heat > shield. > > > On 4/4/07 5:39 PM, in article > Pridnd5h_L-ctInbnZ2dnUVZ snipped-for-privacy@comcast.com,
> > > Got a problem with my 1999 Mazda B2500 (Ford Ranger under > the hood), and > > before I take it to my "plug it into the computer, no error > codes, nothing's > > wrong with it" mechanic, I wanted to run it by some people > that know a > > little more about vehicles. Here's the basics of my truck & > the problem > > > > 1999 Mazda B2500 > > 4-cylinder engine > > 5-speed manual transmission > > 130,000 miles +/-, original everything (including clutch) > > 2-wheel / rear wheel drive > > > > Problem: vehicle makes a metallic chattering sound (like > someone with steel > > dentures chattering their teeth in the cold, best way I can > describe it, or > > maybe like a dime rattling around in an empty beer can) > intermittently. > > Sound seems to be coming from under the floor boards, close > to the back end > > of the vehicle. Sound is worst when there is a load on the > engine, > > especially in higher gears & when going up hill, or if I let > the clutch out > > too slow when up shifting to a higher gear. Sound only > happened once when > > there was no load on the engine. Engine sounds are normal, > engine idles > > within normal parameters (500-750rpms), accelerates well > both on flats and > > up hill. No idiot lights have come up on my panels (and > this truck is like > > a nervous child, if it thinks even the slightest thing MAY > be wrong, my dash > > lights up like a Christmas tree). Sound happens more often > at lower RPMs > > (just before I down shift) or when accelerating suddenly. > > > > I had chalked it up to an old vehicle with a loose panel or > something else > > that's pointless to worry about, until today when a friend > (and former > > mechanic) said it may be something in the driveshaft and/or > rear > > differential. At first I thought the worst this could be > was that my > > 130,000 mile clutch is finally giving out on me, even though > it feels ok. > > When he mentioned this, I had nightmare images of a bearing > seizing up and > > my transmission blowing out as a result. > > > > Obviously to diagnose a problem, it helps to be IN the > vehicle, but anybody > > want to shed some light on the above? Feel free to ask for > more info. I'm > > just trying to get some feedback & suggestions before I take > Chicken > > Little's advice about the sky (and my driveshaft) falling. > > > > C. > > > >
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wrote:

I had the same sound on my '91 Ranger 4x4 until the heat shield fell off in an intersection. Solved the sound problem! ;-)
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From your description of the noise it sounds like you may have a bad u-joint. Put the trans in neutral, apply the parking brake and crawl under the truck to inspect the u-joints. Check for slop in the u-joints but also check for rust were the u-joint cross goes into the bearing caps. If you find either condition replace the u-joints. I am thinking you will find they are rusty and that is causing your noise.
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I agree, it sounds like it is in the driveshaft or differential.

First thing, jack the car up. Grab the driveshaft and push it forward and back, then right to left. Do you feel any play in it? Do the same for the axles. --scott
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On Wed, 4 Apr 2007 18:39:11 -0400, "Chicken-Fried Steak"

The heat shield is loose on your Cat converter or the converter core has melted. Most likely the heat shield.

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Good suggestions. I was going to suggest he inspect the piping and brackets, making sure theyre not broken and that the bushings are intact. Also, your catalytic converter(s) may be getting exhausted (no pun intended!). When I bought my 1998 Camaro, I had a rattling that sounded much like what youre describing under my floorpans, and only at either low RPM (when the engine runs rougher) or on quick accelerations. Try to listen at the converter for the sound.
"Chicken-Fried Steak" wrote: > Got a problem with my 1999 Mazda B2500 (Ford Ranger under the > hood), and > before I take it to my "plug it into the computer, no error > codes, nothing's > wrong with it" mechanic, I wanted to run it by some people > that know a > little more about vehicles. Here's the basics of my truck & > the problem > > 1999 Mazda B2500 > 4-cylinder engine > 5-speed manual transmission > 130,000 miles +/-, original everything (including clutch) > 2-wheel / rear wheel drive > > Problem: vehicle makes a metallic chattering sound (like > someone with steel > dentures chattering their teeth in the cold, best way I can > describe it, or > maybe like a dime rattling around in an empty beer can) > intermittently. > Sound seems to be coming from under the floor boards, close to > the back end > of the vehicle. Sound is worst when there is a load on the > engine, > especially in higher gears & when going up hill, or if I let > the clutch out > too slow when up shifting to a higher gear. Sound only > happened once when > there was no load on the engine. Engine sounds are normal, > engine idles > within normal parameters (500-750rpms), accelerates well both > on flats and > up hill. No idiot lights have come up on my panels (and this > truck is like > a nervous child, if it thinks even the slightest thing MAY be > wrong, my dash > lights up like a Christmas tree). Sound happens more often at > lower RPMs > (just before I down shift) or when accelerating suddenly. > > I had chalked it up to an old vehicle with a loose panel or > something else > that's pointless to worry about, until today when a friend > (and former > mechanic) said it may be something in the driveshaft and/or > rear > differential. At first I thought the worst this could be was > that my > 130,000 mile clutch is finally giving out on me, even though > it feels ok. > When he mentioned this, I had nightmare images of a bearing > seizing up and > my transmission blowing out as a result. > > Obviously to diagnose a problem, it helps to be IN the > vehicle, but anybody > want to shed some light on the above? Feel free to ask for > more info. I'm > just trying to get some feedback & suggestions before I take > Chicken > Little's advice about the sky (and my driveshaft) falling. > > C.
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