Vibration/rattle sound on Right Side Rear (Page 1/2)
Bachman SEP 28, 11:24 AM
Greetings,
I have a 1986 Fiero SE with the V6 and manual trans. I've had an annoying vibration/rattle sound that is sort of a metallic dull rattling which appears to be metal on metal in characteristic. Yikes. No crystal ball here either!!!! It has gotten worse over time but has really pronounced after a garage did a wheel alignment and had to adjust both front and rear alignment. They actually did an alignment and I had to take it back because they made the alignment worse causing the car to drift to the left and I had to steer right using excess steering input to keep going straight. Anyway. Upon getting the car it back from the shop the second time, the vibration has gotten worse, so I'm leaning towards right rear suspension. Then again it could be the coolant pipes related on the right side. I removed the converter heat shield to help isolate the issue but that made no difference. I guess after all this explanation, I'm hoping someone has already had this issue and has found the problem to remedy the issue. Also, the A/C compressor has internal mechanical issues and the clutch has created a screaming high pitch sound when I was diagnosing sensors as the problem for lack of clutch engagement. Easy enough to remove the A/C belt, well, not that easy, but to help with the diagnosis of the metallic rattling sound. Standing still the car does not make an vibration when increasing and decreasing the rpm's. It almost feels like a tire on roadway issue through the suspension and vibrating through the body.
To help in understanding road conditions etc, the sound is really pronounced at about 40 to 42mph and 1800 rpms on a straight smooth highway. I've opened the passenger door while driving and can really hear the sound. I can tickle the throttle pedal to created a difference in the sound.
Thank you so much for you insight and help.
Cheers, Dave
Bachman OCT 05, 02:55 PM
I am responding to see if this post is recognizable by others and able to respond.
theogre OCT 05, 08:42 PM
Can be a lot of things...

Example: A dirt shield hitting a brake rotor is common but several reasons make that happen and can be more than one @ same time. top 3...
Bent shield
Rotor replace from iffy source and Hat area hits.
Wheel/Hub bearings are bad.

Wheel/Hub bearings Do Not like Preloading or being too loose. See my Cave, Front Bearings but rear hubs just be bad or someone over/under torque an axle nut can do same.

Several heat shield and exhaust parts in the engine bay can make a lot of noise when car is sitting, moving or both. Worse if have bad engine and trans mounts.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Bachman OCT 15, 11:16 PM
Thank you for your insight. I have been having A/C issues. I try to charge the system and the clutch locks up. I was thinking it's a defective compressor seized up. Thought more about the sound it makes and being a engine rpm related issue at 1800 rpms. With the A/C compressor not engaging, A/C turned off, I'm thinking it's the bearings in the A/C clutch unit causing a specific frequency vibration creating the noise I'm hearing. I removed the A/C belt and the A/C compressor turns over quite easily. So now I need to drive the car and try to re-create the noise at 1800 rpms and 40ish mph. If it's gone, I need to remove that compressor and have a closer look at the clutch and no doubt replace it. The car only has 44K miles on it, so A/C compressor should be OK. Used to cool like a meat locker. I'll get back to you after I road test tomorrow.
Bachman OCT 18, 08:28 PM
Well, it wasn't the A/C clutch bearing. I think it's a plastic body panel issue. Seems to be on right behind the door but hard to tell while driving. It happens at 30-32 MPH regardless of engine RPMS. Has anyone had issues of a rattling sound from body panels that can help me out. Drives me nuts. Hey, it's a plastic body!!!! Corvette has same thing going on as I recall.
Gall757 OCT 19, 02:44 PM
Re-balance your tires.
Bachman OCT 19, 03:48 PM
Tires are brand new and has had 4 wheel alignment a month ago. I've had this annoying rattle awhile now and prior to new tires and alignment and need to find it and cure it. It seems like a body panel vibration on the passenger side only. It appears to be created by the road vibrations through the suspension and the rest of the car components which I'm leaning towards a body panel issue as it's not a metal on metal sound. It is pronounced at 30 to 32 MPH and also associated to RPM at that speed. I can hear it also with the trans in neutral and coasting down a hill. Very strange!!!! Any advice would be greatly appreciatred.
Cheers
Gall757 OCT 19, 04:26 PM
Maybe it's your output bearing in the transmission. Grab the axle close to the trans and push-pull to see how much movement there is. More than an eighth of an inch allows the axle to vibrate under the right conditions.
Bachman OCT 19, 08:57 PM
Thanks for the heads up. I'll jack it up and give it a go. Cheers
Bachman OCT 19, 09:00 PM
It just seems so strange to on happen only in a two MPH range and not continuous if a bearing were bad. If I tap on the plastic rocker panel it creates what I hear while driving. It's a frequency created sound at a specific MPH.