whistling noise

[gatorman21218]

After a moderate acceleration (~2500 rpm), when I push in the clutch to grab another gear, the truck whistles as the rpms drop. Its almost like a turbo winding down, yet I dont have one of them buggers. I'm thinking maybe a throw out or pilot bearing? A few weeks ago I knocked off a return line and a few gallons of diesel ran down the back of the engine and bell housing. Could that have washed all the grease away? http://www.oilburners.net/forums/showthread.php?t=42022
I dont really hear the whistle at any other time, but it could be there, my exhaust is so loud its hard to hear much of anything How does one check these bearings? Any other thoughts?

 

[gatorman21218]

bump

 

[Jake_IN]

Well this probably isn't it but just throwing it out there. Ive had that sound before too and it turned out to be from the radio picking up the alternator. A very faint whistle would come from the speakers whenever i accelerated. It would go away if ya turned the radio off. Doubt that's it but just thought I would throw it out there.

 

[Worstenemy453]

Well this probably isn't it but just throwing it out there. Ive had that sound before too and it turned out to be from the radio picking up the alternator. A very faint whistle would come from the speakers whenever i accelerated. It would go away if ya turned the radio off. Doubt that's it but just thought I would throw it out there.

Alternator whine. Technical name for that.

 

[david_lee]

Well this probably isn't it but just throwing it out there. Ive had that sound before too and it turned out to be from the radio picking up the alternator. A very faint whistle would come from the speakers whenever i accelerated. It would go away if ya turned the radio off. Doubt that's it but just thought I would throw it out there.

Alternator whine. Technical name for that.

i believe thats actually called a ground loop. a ground loop can usually be solved with a dedicated ground wire from the component to the battery, but most people use a ground loop isolator, which is basically a filter for that particular electrical component.

if you are experiencing a ground loop after a spill of diesel, you might want to check your cab ground connections.

 

[Worstenemy453]

i believe thats actually called a ground loop. a ground loop can usually be solved with a dedicated ground wire from the component to the battery, but most people use a ground loop isolator, which is basically a filter for that particular electrical component.

if you are experiencing a ground loop after a spill of diesel, you might want to check your cab ground connections.

They are different but a ground loop will cause alternator whine. Usually in aftermarket systems, surprisingly, alternator whine occurs more in GM vehicles than Fords. Thats not bs either.

This is a ground loop

II. Don't introduce ground loops. Ground loops are created whenever an audio ground is established at more than one location. Theoretically, the only place the audio ground should be connected to the chassis ground is at the source unit. In my experience, I've found that in systems that have noise problems, a ground loop is the culprit nine times out of ten.

Alternator Whine

To me, alternator whine is the most annoying form of noise. For those of you who are lucky enough never to have been exposed to alternator whine, it sounds like a miniature siren that rises in pitch with the speed of the engine. Alternator whine is almost always caused by a ground loop. The following steps will aid you in locating and correcting a ground loop problem.

Finally Here is some steps to remove Alternator whine.

1) Verify that all levels are set properly. (Click here for related article.)
2) With the system turned off, unplug the RCA inputs to the amplifier.
3) Start the vehicle and turn the system on. If the noise is gone go to step 8. If the noise is still present, it is coming from the amp or the speaker wiring. Continue.
4) Turn the system off and disconnect the speaker harness.
5) Start the engine and verify that no noise is present. In a few rare instances, I have actually heard speakers reproduce noise without being connected to an amplifier. This noise was being induced by power cables that were very close to the speaker wire. If you do have this type of noise, reroute the appropriate speaker lead and go to step 3.
6) With the speaker harness still disconnected, check to make sure there are no shorts between the speaker leads and the chassis of the vehicle. A shorted negative speaker lead will create a ground loop by establishing a second audio ground reference point. If you do have a short, trace the wire out and repair it then go to step 3.
7) With the RCA inputs and speaker harness still disconnected from the amplifier, use your VOM to measure from the shield of the RCA jacks on the amp to the chassis of the vehicle. This reading should not be a direct short (100 ohms or more is acceptable.) If this reading does indicate a direct short, you might have a defective amp and should contact the manufacturer for verification. (Note that there are a few "inexpensive" amps or boosters on the market that have their audio ground and electrical ground commoned internally. For units of this type, the information in this article will be of very little value.)
8) If you've made it here, you know that the amplifier and speaker wiring are okay.
9) Connect the accessories in front of the amp (crossovers, equalizers, etc.) one at a time and check for alternator whine. When each device is tested, there should be nothing plugged into the input of that device. In this way, we will work toward the source unit piece by piece. Be sure to turn the system power off before connecting or disconnecting any cables or accessories.
10) Repeat step 9 until all accessories have been tested.
11) If a particular accessory is causing noise, try disconnecting it's power ground wire. Go to step 9.
12) Now it's time to connect the source unit. Do that now and test for noise.
13) If noise is present, try unplugging the antenna. If the noise goes away, you will need to use an antenna isolator. This little gismo opens the shield wire of the coax to eliminate the ground loop caused by the ground at the antenna.
14) If you still have noise, try connecting the source unit's ground wire in another location,. preferably as close to the source unit as possible.
15) Does the noise vary in amplitude when you adjust the volume control? If it does, the problem is probably power line related and not a ground loop. If this is the case, run the source unit's B+ (yellow) wire directly to the positive terminal of the battery. If this doesn't do the trick, you will probably have to use a power line filter on the source unit's B+ (Yel) and Ignition (Red) wires.

 

[david_lee]

They are different but a ground loop will cause alternator whine. Usually in aftermarket systems, surprisingly, alternator whine occurs more in GM vehicles than Fords. Thats not bs either.

This is a ground loop


Alternator Whine


Finally Here is some steps to remove Alternator whine.

i have corrected that whine a time or two with an improved ground at the head unit, but those were not amplified systems. according to your info, either that issue was antenna ground related or there was something else going on.

 

[Timthetoolman]

Mine did that, the exhaust manifold was loose, finely blew the gasket.

 

[gatorman21218]

Well I definently do have alternator whine. I cant listen to AM at all when the engine is running. however it does it when a cd is playing. I screwed up my cb power last night messing around with the fuses and it was off today and I didnt notice the whining. I will go check the grounds to make sure. BTW I have an amplifier for my radio