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9/5/17 1:36pm - Original Message: 'metallic rattle sound'
jgoglick Lifetime Member
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Huntsville, AL - USA

Vette(s):
1971 convertible,375 HP 350ci,Muncie 4-speed,Edelbrock aluminum heads and RPM air-gap manifold,HEI distrubiter - old school mechanical tach drive. LOUD side exhaust!

Joined: 11/15/2003
Posts: 840
So, yes, I'm alive.....Admittedly, the vette has not gotten a ton of use the past few years. But at least this year that has changed. I've driven it much more often. I've got most of the interior reinstalled (no, most of the crap still doesn't work - wipers, I'm looking at you) but I don't care. Have to have at least ONE project for later, right? I did get some nice new Torque Thrust II wheels and new tires (17"). Such a huge difference!
 
So, on to the reason for the post. This noise started happening before the new wheels and tires, btw. When the car is cold, I hear what sounds like a metallic sound - not a clicking, but not a banging either - from the left rear. I notice it in first and second gear, and maybe faintly in third - hard to tell with wind noise after that. After driving for several minutes, the noise disappears. It doesn't act like a bearing - the noise is not dependent on turning - it happens equally when going straight or turning with no change.
Things I've looked at:
 
1. I thought maybe it was a trim piece loose and flapping. No, and would continue at all times, not just when cold.
 
2. Another reach - the rod (maybe not the correct term) on the calipers that connects them on the top had some play in it. I adjusted the cotter pin to get rid of the play. The noise is still there.
 
3. I put the car on the lift and had the wife put it in first gear and spin the wheels. I didn't hear the noise at all (engine was cold).
 
 
So. Is it a wheel bearing? U joints (they look ok)? Or the diff? Or something else to look at? My diff does seep fluid. I have lube and posi additive coming from Amazon. I'll do a fluid change this weekend - way overdue no matter what. I also know that I really need to rebuild the diff. That will come this winter, hopefully, along with the trailing arms.


|UPDATED|9/5/2017 11:36:30 AM (AZT)|/UPDATED|
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9/5/17 4:25pm - Reply: 'Re: metallic rattle sound'
johnu
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Eagan, MN - USA

Vette(s):
1981 Corvette Two-Tone Claret color, 4 spd, C7 Vert

Joined: 5/23/2007
Posts: 507
It it your heat riser?  Located on the exhaust manifold before the pipe.... Mine flips around and makes noise for about a city block as it warms up and opens.

|UPDATED|9/5/2017 2:25:32 PM (AZT)|/UPDATED|


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9/5/17 4:32pm - Reply: 'Re: metallic rattle sound'
jgoglick Lifetime Member
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Huntsville, AL - USA

Vette(s):
1971 convertible,375 HP 350ci,Muncie 4-speed,Edelbrock aluminum heads and RPM air-gap manifold,HEI distrubiter - old school mechanical tach drive. LOUD side exhaust!

Joined: 11/15/2003
Posts: 840
Nope. Coming from the left rear, and I have side pipes.

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John

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9/5/17 9:23pm - Reply: 'Re: metallic rattle sound'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19454
Good to see ya back on the Forums, John...been a while! Big smile
Does this noise sound like possibly a scraping noise? Grind? Rattle? Squeak? Does is sound like a sheet metal(tinny) noise, or something heavier?
It's possible it could be a wheel/hub bearing...they can make all sorts of different noises, depending on what is actually failing. Since you couldn't get it to make a noise with the rear suspension in the air, that sorta makes me think it is in the wheel/hub/rotor area. The reason being that there is no real pressure on the hub bearing(s), or brakes at that point. A u-joint noise would have at least changed with it in the air....raising the rear and running it in gear puts a tremendous strain/pressure on the outer u-joints.
It's very possible that a bearing is loose, and the rotor is rubbing somewhere on the caliper, even tho the noise seems to go away after a few miles. Might even be the rotor rubbing on the backing plate.
If you can, get the rear back up in the air, and check for ANY play in the hub bearings on the left side by grabbing the wheel/tire at the 12 & 6 o'clock positions, and push(top)/pull(bottom) in/out, and see if there is any noticeable play. You might need someone to look under the car directly at the u-joint flange on the hub(where the axle bolts up) to see if that flange is moving. Mind you, there will prolly be some play in the axle yoke where it goes into the diff, but we're not looking for that at this point. We want to see if the flange is moving independently from the spindle support. Ideally, you want to see/feel absolutely NO play there. A bad/loose bearing will show up by watching the flange move as you wiggle the tire/wheel assy.
hthSmile

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Joel Adams
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9/5/17 9:42pm - Reply: 'Re: metallic rattle sound'
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 394
If you have a baffled insert in the side pipes, it could be a loose baffle.

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1973 L-82 4 spd

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9/6/17 7:07am - Reply: 'Re: metallic rattle sound'
jgoglick Lifetime Member
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Huntsville, AL - USA

Vette(s):
1971 convertible,375 HP 350ci,Muncie 4-speed,Edelbrock aluminum heads and RPM air-gap manifold,HEI distrubiter - old school mechanical tach drive. LOUD side exhaust!

Joined: 11/15/2003
Posts: 840
Thanks for the responses guys Handshake
 
The sound is definitely metallic - as if two pieces of metal are banging against each other. I drove it to work this morning. I backed out of the garage and pulled into the road. Into first, and the sound is there. But here is an addition....it's only there while accelerating. Tested it out going down the neighborhood...I'm sure the neighbors loved that at 5:50 A.M. Shocked Anyways, I pull out of the neighborhood and drive about 3 miles and get stopped at a light. I pull out and the noise is gone. So, I'm fairly confident it's the insert in the side pipe rattling and it goes away once it heats up and expands (thanks for the suggestion Marc!)
 
I'm still going to look at the wheel bearings this weekend...just to make sure - thanks Joel! Clap


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John

C3VR Lifetime Member #78


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