Random clacking from bell housing area when in park/ neutral.

[Oliver Closehauf]

I've noticed a random clacking noise from what sounds like the bell housing when idling in park or neutral. When I shift into drive or reverse the clacking stops. I have not driven the truck much since I bought it in November, but never noticed any problem or balance issue.

Before I pull the flywheel cover and check for a loose torque converter, I thought I would ask if this a typical noise for a diesel. The tranny has Goerend internals, but it also has 275K on the truck.

 

[Oliver Closehauf]

Just to follow up, the tranny was rebuilt at 210k and serviced at 225k. I got the info from the P.O. so I guess I'll take it back to that shop if I find that the converter is tight.

 

[Oliver Closehauf]

OK, so I didn't find anything glaring after removing the cover.

A few youtube videos later, if the comments I read are accurate, this is not the tranny, but the computer killing cylinders randomly under no load to help the engine warm up faster? Just sounds like it's coming from the tranny.

Everything is quiet (for a diesel) when in gear, and it runs fantastic, so I'm just going to add it to the list of odd noises diesels make.

 

[crash68]

A few youtube videos later, if the comments I read are accurate, this is not the tranny, but the computer killing cylinders randomly under no load to help the engine warm up faster? Just sounds like it's coming from the tranny.

Everything is quiet (for a diesel) when in gear, and it runs fantastic, so I'm just going to add it to the list of odd noises diesels make.

They don't kill cylinders to help warm up a diesel, you have to put them under a load or elevated idle to warm them up. With later versions of CTD you can use the cruise control buttons to elevate the idle while parked. With a diesel you idle it to cool it down, especially when working the engine hard.

 

[Oliver Closehauf]

Well, the info I was able to come up with is it is injector related, and not tranny related. If it's on purpose or not, I have no idea. I'm just glad it's not the transmission.

Why injectors would randomly do something at idle that would cause that clacking is a whole different mystery to solve. Any ideas?

Watching people drone on and on in youtube videos before they get to the point gets old fast.

 

[crash68]

Why injectors would randomly do something at idle that would cause that clacking is a whole different mystery to solve. Any ideas?

Most likely it's not the injectors themselves but the actual combustion process, that can be effected by engine temp, atmospheric conditions, fuel quality, etc.
With a diesel the cylinder is compressed then the fuel is injected in where the superheated compressed air ignites the fuel, unlike a gas engine where the fuel and air is compressed then ignited by a spark plug. Engineers can control the noise of combination by how much and when the fuel is injected, sometimes referred to pilot injection.
Cummins prior to the '19 model year didn't do much pilot injection for noise control.

 

[yoda]

The you tube videos you were watching may have been referring to the previous gen. 24 valve cummins. 1997-2002
You could enable it to idle on 3 cylinders when the engine was cold to help it warm up faster. There was a PCM flash, then you had to enable the feature with the DRB 3 scan tool.
It never really worked that well in my opinion
The idea was to put more load on the engine to help it warm faster, never really made sense to me as the cylinders that were not firing were pumping cold air through the engine

 

[Oliver Closehauf]

Surprise follow up. I just changed my fuel filter and the clacking is gone. So apparently it was injector related somehow. Maybe some crap in a line that was able to backwash out during the whole change process. I wasn't expecting it, but it was a nice surprise. The filter that was in there didn't look that bad and the engine ran great except for that random clacking at idle.
I spent way more time researching the problem than it took to actually fix it.