Loud chirping noise

Dougbob · **Posted:** Sat Jul 04, 2020 1:05 pm

So I started getting a loud chirping noise. It is similar to what I would normally expect when a throw out bearing is going bad. Except it only makes the noise in two situations. the first is when I let off the throttle and it chirps once when the motor just starts using back pressure to slow. the other time is when you are trying to maintain a constant speed, and just slightly let off the throttle just a hair. I can not recreate the issue when the vehicle is sitting still. I started getting this issue about 5 days after replacing the Alternator. But I don't see how it could be the alternator making this noise...... To me it seems to only make this chirping noise when the turbo goes from boost pressure to back pressure..... But i pulled the air intake hose off the turbo, and I'm not feeling any play in the turbo shaft...

Any Ideas?

WolverineFW · **Posted:** Sat Jul 04, 2020 1:14 pm

Take the serpentine belt off and run the engine. Rev it up and see if the noise is there without the new alternator.

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WWDiesel · **Posted:** Sat Jul 04, 2020 1:56 pm

Dougbob wrote:

So I started getting a loud chirping noise. It is similar to what I would normally expect when a throw out bearing is going bad. Except it only makes the noise in two situations. the first is when I let off the throttle and it chirps once when the motor just starts using back pressure to slow. the other time is when you are trying to maintain a constant speed, and just slightly let off the throttle just a hair. I can not recreate the issue when the vehicle is sitting still. I started getting this issue about 5 days after replacing the Alternator. But I don't see how it could be the alternator making this noise...... To me it seems to only make this chirping noise when the turbo goes from boost pressure to back pressure..... But i pulled the air intake hose off the turbo, and I'm not feeling any play in the turbo shaft...
Any Ideas?

What alternator part number did you put on the engine?
Does it have the one-way override pulley on it? Sounds like based on your issue; it does not.
Also note, a weak or work out belt or belt tensioner can also cause "chirping".

Many use this OAD Pulley: Litens 920720A

What does an OAD™ pulley do? wrote:

An OVERRUNNING ALTERNATOR DECOUPLER™ pulley helps "synchronize" the belt drive system for improved engine efficiency, reduced Noise/Vibration/Harshness (NVH) and increased component life.

When an engine accelerates, the alternator's mass creates resistance against the belt. In addition, due to differences in drive ratio between the crankshaft and alternator pulleys, alternator speed is typically three times faster than engine speed. These factors often cause "rope-tow effect" in which belt speed and alternator speed are out of phase. Belt tensioners can absorb some of the resulting vibration, but the belt ultimately bears the brunt of this damaging force.

An OAD™ pulley features a sophisticated internal spring and clutch system that absorbs the force associated with belt accelerations and tension reversals and permits the alternator to "free-wheel" or "overrun" when the belt suddenly decelerates.

It should look like this on your alternator with a plastic cap over the end of the pulley if it is a OAD pulley.

geordi · **Posted:** Sat Jul 04, 2020 5:58 pm

If your serpentine tensioner is bouncing at idle, then YES, it is the alternator pulley. Just b/c it is "new" does not (sadly) mean that they sold it with a decent pulley or even the right one.

Also... Diesels don't have backpressure to slow down with. The engine is a continuous duty air pump, the air is ALWAYS going the same direction through the engine, the change in power / drag you are feeling is when the fuel flow is cut completely. Unless you've installed an exhaust brake on it, there is virtually no pressure in the exhaust system b/c after the turbo there are no significant restrictions.

Dougbob · **Posted:** Sat Jul 04, 2020 7:53 pm

so yes the alternator does have an OAV pulley. I took the belt off and Drove it around the block, and it still makes the chirping noise.

Dougbob · **Posted:** Sat Jul 04, 2020 7:57 pm

WolverineFW wrote:

Take the serpentine belt off and run the engine. Rev it up and see if the noise is there without the new alternator.

Sent from my SM-G965W using Tapatalk

It doesn't make the noise when idling, or when parked and reving the engine. I pulled the belt and drove it around the block and it still made the noise. I'm also considering that it may be a driveline U-joint, Other than i replaced all of them 2 years ago, and really don't want to replace them all again to it not be that.

WolverineFW · **Posted:** Sat Jul 04, 2020 9:03 pm

Could be a bad CV joint...maybe....

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ebbnflow · **Posted:** Sun Jul 05, 2020 7:11 pm

Dougbob wrote:

WolverineFW wrote:

Take the serpentine belt off and run the engine. Rev it up and see if the noise is there without the new alternator.

Sent from my SM-G965W using Tapatalk

It doesn't make the noise when idling, or when parked and reving the engine. I pulled the belt and drove it around the block and it still made the noise. I'm also considering that it may be a driveline U-joint, Other than i replaced all of them 2 years ago, and really don't want to replace them all again to it not be that.

I just replaced my drive shaft u joints. Had a chirping sound when I let off the gas. Crawled under and drive shaft was really hot near the front u joint. Pulled rear drive shaft. U-joint was shot. Replaced it and all is better.

farmnfly · **Joined:** Fri Apr 08, 2011 10:22 pm **Posts:** 20

I had a similar issue took for ever to fine, ended up being the harmonic balancer. The main drive pulley on the engine. here is the youtube link www.youtube.com/watch?v=IRPMs42c3QQ

Dougbob · **Posted:** Thu Jul 09, 2020 9:14 pm

So I finally got my jeep up in the air on a lift, and ran it. Turns out the Carrier Bearing in my rear end is bad......... :furious:

geordi · **Posted:** Fri Jul 10, 2020 10:17 pm

At least you've found it, and it isn't a CRD-specific issue... So the parts shouldn't be hard to find!

03black · **Posted:** Sat Jul 11, 2020 1:28 am

Parts are readily available..chrysler 8.25 rear end. Just get a rebuild kit, has everything you need to freshen up the rear differential minus the axle seals and bearings but good time to do those as well since you have it all torn apart.

You'll need the special bearing adjustment tool if you do the job yourself, or you can make one. Otherwise take it to a professional shop to have done.

Loud chirping noise

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