Strange Knocking Sound

[jeeper4life73]

The video in this post is from a 2019 JLU MOAB. It's lifted, 3.5in, running 37s. The dealership can't figure it out. I've checked everything i know to check. The knocking sound is present when you are between 8 to 21 mph and only when you let of the gas, slowing down. As soon as you accelerate, even the slightest bit, it stops, but if you let of the gas it immediately starts back up. It is not present in either case, if raised off the ground. The weight of the Jeep must be on the ground to produce the sound. I can feel the knocking ever so slightly in both the steering wheel and the brake pedal. I already removed the front drive shaft and the knock was still there.

If anyone has any recommendations or questions let me know.

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[N875ED]

Is this noise from the front or rear? If the rear (and this is a long shot), investigate the parking brake components. It uses a pair of brake shoes working inside the rear rotors, and a shoe retaining pin being loose just might cause the shoe to knock like that on deceleration.

 

[calemasters]

I was thinking the front or rear U-joint on the rear drive shaft. Also check the lug nut torque.

 

[aldo98229]

I agree, sounds like it is driveshaft-related.

Noises that come and go when the engine power load changes are normally related to a driveshaft.

The 8-21 MPH thing probably relates to the speed at which the driveshaft spins.

If it happens all the time, it is likely the rear shaft; if it happens only in 4WD, it is likely the front shaft.

Good luck.

 

[Glamisfan]

Drivshaft/ujoints would be my first guess. Said said you can feel it through the steering wheel song most likely in the front end. Could be a ring and pinion. i’ve had something similar happened in a big rig where accelerating or cruising it would be fine but when you let off the throttle it had a knock in the rear end.

 

[jeeper4life73]

I agree, sounds like it is driveshaft-related.

Noises that come and go when the engine power load changes are normally related to a driveshaft.

The 8-21 MPH thing probably relates to the speed at which the driveshaft spins.

If it happens all the time, it is likely the rear shaft; if it happens only in 4WD, it is likely the front shaft.

Good luck.

Thank you for the reply. I will look into the e brake idea mentioned previously. According to the dealership they said they checked and re-torqued everything...I have my doubts about that as with anything the dealer can't figure out. It makes the exact same noise in 4WD or 2WD. And I've already tested removing the front shaft. My next thought was to remove the rear shaft and drive in 4WD and see if it's still there. That should rule out drive shaft issues. The sound is present when the Jeep is cold or after driving awhile.
Thanks again.

 

[mwilk012]

remove the rear drive shaft and put it in 4wd.

 

[jeeper4life73]

remove the rear drive shaft and put it in 4wd.

Yup that's the next move. I'll follow up if it is the culprit.

 

[sn3akyducky]

It might be in your rear differential. It sounded just like mine and the dealership replaced a series of components till they found it to be the rear diff assembly. I think they did a ring and pinion.

 

[JeepersCreepers2]

It might be in your rear differential. It sounded just like mine and the dealership replaced a series of components till they found it to be the rear diff assembly. I think they did a ring and pinion.

This. Had the exact same issue and it’s the rear Dana 44. Had multiple things replaced along with ring and pinion. All good now

 

[jeeper4life73]

I'm pretty sure now after hooking up a camera underneath in various areas the sound is coming from the rear diff, as many fellow Jeepers have pointed out. In the up front videos the sound can barely be heard, but the attached video is the rear axel. If I can get the dealership to ever call me back to discuss options to get this fixed we might actually get somewhere.

 

[Maverick909]

sounds like a bad clutch pack in the LSD. or something is loose thats pretty bad. id take the video to the dealer as well

 

[trurob777]

The video in this post is from a 2019 JLU MOAB. It's lifted, 3.5in, running 37s. The dealership can't figure it out. I've checked everything i know to check. The knocking sound is present when you are between 8 to 21 mph and only when you let of the gas, slowing down. As soon as you accelerate, even the slightest bit, it stops, but if you let of the gas it immediately starts back up. It is not present in either case, if raised off the ground. The weight of the Jeep must be on the ground to produce the sound. I can feel the knocking ever so slightly in both the steering wheel and the brake pedal. I already removed the front drive shaft and the knock was still there.

If anyone has any recommendations or questions let me know.

Sounds like your rear DIFF is knocking. Does the MOAB edition have the Limited Slip Dana 44?

I think you have the issue on this thread: https://www.jlwranglerforums.com/forum/threads/knock-in-rear-with-dana-44.16921/page-88#post-1326900

My Sport S with the Limited slip rear has had this noise as well.

 

[mmai]

I'm pretty sure now after hooking up a camera underneath in various areas the sound is coming from the rear diff, as many fellow Jeepers have pointed out. In the up front videos the sound can barely be heard, but the attached video is the rear axel. If I can get the dealership to ever call me back to discuss options to get this fixed we might actually get somewhere.

Did you ever end up figuring out what was causing the noise? I am hearing it on mine from the rear as well and it sounds like the video you posted.

 

[jeeper4life73]

Apparently there was something serious enough to warrant a full rear diff rebuild by the dealership. Never really explained what the actual problem was or the cause. But whatever this defect is caused me to have to get the front diff rebuilt as well not long after.
Side note: make sure you check the torque specs on any diff cover removed by the dealership. Several of the diff bolts were barely hand tight on both diff covers after I checked them after the break in.

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