3.6l Crank Pulley Runout?

[Reflektr]

I’ve been experiencing a “knock” or a harsh rattle when I shut off my Jeep. It’s done it since day one and I have been told “not to worry about it” but I can’t leave well enough alone lol. I popped the hood tonight with the engine running and noticed the crank pulley seems to have an abnormal amount of runout? Not sure if you can tell from my phone video or not, but is this normal, or am I onto something here?

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[alphawolff]

You need to post a video of the noise

 

[Reflektr]

You need to post a video of the noise

This is about the best I can provide at the moment. I’m not sure what the little “ting” is at the end, but the noise that I’m wondering about is more of an abrupt “clunk” and shake when I shut the engine off. Like when an engine mount goes bad. I’m not sure if being a manual transmission is a contributing factor, but I’ve tried shutting it off with and without the clutch pressed and it doesn’t change anything.

 

[alphawolff]

This is about the best I can provide at the moment. I’m not sure what the little “ting” is at the end, but the noise that I’m wondering about is more of an abrupt “clunk” and shake when I shut the engine off. Like when an engine mount goes bad. I’m not sure if being a manual transmission is a contributing factor, but I’ve tried shutting it off with and without the clutch pressed and it doesn’t change anything.

My manual 3.6l makes this exact same noise on shutoff frequently enough

 

[Reflektr]

My manual 3.6l makes this exact same noise on shutoff frequently enough

Thank you. Is this another one of those “Jeep Things”? I am not super familiar with Wranglers, but I am familiar with 3.6l Pentastars. None of the 3.6 Liters we have at work do this, nor do my wife’s Cherokee or Grand Cherokee. I just had a Ram 1500 in my shop with the 3.6l (insert massive eyeroll ) and the shutdown was smooth and there was no wobble coming from the harmonic balancer either.

If it’s not hurting anything then I guess I won’t worry about it. But what I may do to satisfy my curiosity is try and track down another new v6 manual and see what it sounds like.

 

[alphawolff]

Thank you. Is this another one of those “Jeep Things”? I am not super familiar with Wranglers, but I am familiar with 3.6l Pentastars. None of the 3.6 Liters we have at work do this, nor do my wife’s Cherokee or Grand Cherokee. I just had a Ram 1500 in my shop with the 3.6l (insert massive eyeroll ) and the shutdown was smooth and there was no wobble coming from the harmonic balancer either.

If it’s not hurting anything then I guess I won’t worry about it. But what I may do to satisfy my curiosity is try and track down another new v6 manual and see what it sounds like.

It just sounds like a hard fuel cut. Go turn off a 6.7L cummins and it'll make the same weird clunk. Instead of it "gracefully" shutting off it just stalls out instead.

But yeah, don't worry about it. The difference with the manual is the engine has less load (rotating mass of the torque converter in an auto) during shutoff. It just makes for some different harmonics.

 

[Reflektr]

It just sounds like a hard fuel cut. Go turn off a 6.7L cummins and it'll make the same weird clunk. Instead of it "gracefully" shutting off it just stalls out instead.

But yeah, don't worry about it. The difference with the manual is the engine has less load (rotating mass of the torque converter in an auto) during shutoff. It just makes for some different harmonics.

I appreciate the input. That does make total sense. Without a big heavy torque converter full of fluid acting as a buffer and all. Just in the same manner the Jeep drivetrain makes funny noises when you load/unload with the clutch and throttle. Getting used to all the noises and quirks of a different vehicle can be nerve-racking lol.

 

[mwilk012]

To the point about that crank pulley, it’s 100% normal.

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