Author Topic: Rotational rear end knock  (Read 362 times)

Offline TuffyMctuffy

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Rotational rear end knock
« on: June 28, 2021, 12:34:38 PM »
Has anyone experience a rotational rear end knocking at los speed, mostly coasting? I have an 18 JLU with the m220 rear and LSD. This first occurred around 9k miles and the dealer was able to recreate the sound, but unable to determine the cause. Their fix was to replace every moving component in the rear. Basically rebuilt the axle and replaced the LSD. This fixed the issue and how fast forward another 10k miles and it had returned. Headed to the dealer to make another appointment today. If anyone has experienced anything similar, I’d love to hear your experience, how you diagnosed it and what the fix was. I’m hoping to take the information and relay it to the dealer to aid in a fix! Jeep has 21k miles on it and I’d hate to be back in the dealer every 10k miles having them replace all the rear end guts. I’m planning a trip to Utah next June and don’t need to be 1800 miles from home and have a rear end failure on a new Jeep!

Offline 3VOLVE

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Re: Rotational rear end knock
« Reply #1 on: June 29, 2021, 05:01:58 PM »
I havent experienced anything like that with my JL, but I am interested to hear what they say this time around.  Keep us posted.

- joe
Joe (3VOLVE) - US Army Veteran
2019 JLUR

Offline BLACKHAWKJEEP

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Re: Rotational rear end knock
« Reply #2 on: June 29, 2021, 10:01:50 PM »
From doing some research it would seem other JLs are experiencing the same issue and the fix from the dealership is to replace axle components but... I am not sure. I am also interested to see what the exact issue/issues could be.

Does it sound like this?
https://www.youtube.com/watch?v=TuGlJnjqrGo

Or similar to?
https://www.youtube.com/watch?v=4tg34qfmtFI

From the comments dealerships are replacing differential components.
I will admit I am not the expert here, but figured I'd ask and get some video proof to see if that's what you are experiencing.

Same with this one:
https://www.youtube.com/watch?v=7xZjXCLdD8U

Comments demonstrated that the owner had the axle replaced with a new one.
« Last Edit: June 29, 2021, 10:07:23 PM by BLACKHAWKJEEP »

"... hey heim-joint, that's your name now!"

Offline R3

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Re: Rotational rear end knock
« Reply #3 on: June 30, 2021, 07:11:19 PM »
Had a vibration in my 3500 dually... Narrowed down to the rear axle...basic part swapping... several time before I got the regional engineer involved... Simple elevate the issue at your dealer...that process is a email back and forth between the dealership and FCA engineering.

If the problem is reoccurring you can go the lemon law route.

Option is go to a reputable shop that knows jeeps back and forth. There are a few I would recommend and a few I would stay away from.





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Cheers

17 JKURR Daily/rock crawler/overland
2013 Victory XCT hot rod.

Offline R3

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Re: Rotational rear end knock
« Reply #4 on: June 30, 2021, 07:17:07 PM »
Another thought is the LSD is somehow binding. Or there is a tolerance issue in the rear.

If they are replacing the rear internals each time there is a break in period... usually 500 miles then inspect. If the dealer has replaced all the guts, and not reinspecting....that might be the issue.

The 500 mile inspect is to check for backlash and any "issues" that might appear.

LSD sets usually require an additive. If it is not added problems ensure.

All I can think of for now.

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Cheers

17 JKURR Daily/rock crawler/overland
2013 Victory XCT hot rod.

Offline TuffyMctuffy

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Re: Rotational rear end knock
« Reply #5 on: July 03, 2021, 06:06:18 PM »
From doing some research it would seem other JLs are experiencing the same issue and the fix from the dealership is to replace axle components but... I am not sure. I am also interested to see what the exact issue/issues could be.

Does it sound like this?
https://www.youtube.com/watch?v=TuGlJnjqrGo

Or similar to?
https://www.youtube.com/watch?v=4tg34qfmtFI

From the comments dealerships are replacing differential components.
I will admit I am not the expert here, but figured I'd ask and get some video proof to see if that's what you are experiencing.

Same with this one:
https://www.youtube.com/watch?v=7xZjXCLdD8U

Comments demonstrated that the owner had the axle replaced with a new one.

It’s actually neither of those. I found a video the first time on another forum of the exact sound. It’s an intermittent rotational knock between 8-13 mph. I can reproduce it by coasting at those speeds and bumping it into neutral. Otherwise it’s intermittent in that weird spot while coasting and not u FDR load from deceleration or acceleration while in gear.

Offline TuffyMctuffy

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Re: Rotational rear end knock
« Reply #6 on: July 03, 2021, 06:08:43 PM »
Another thought is the LSD is somehow binding. Or there is a tolerance issue in the rear.

If they are replacing the rear internals each time there is a break in period... usually 500 miles then inspect. If the dealer has replaced all the guts, and not reinspecting....that might be the issue.

The 500 mile inspect is to check for backlash and any "issues" that might appear.

LSD sets usually require an additive. If it is not added problems ensure.

All I can think of for now.

They went the fluid change and additive route the first troubleshooting session. No joy. Then they went the parts replacement specialist route and joy for 10k miles, now back to square one.

I hate to even discuss lemon law with what I’ve spent to modify it to this point. I do not want to start this build all over again.

Part of the initial troubleshooting was to play with the fluids and the lsd additive. No joy. So they went the parts replacement specialist route. Joy for 10k miles then back to square one.

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« Last Edit: July 03, 2021, 06:11:33 PM by TuffyMctuffy »

Offline TuffyMctuffy

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Re: Rotational rear end knock
« Reply #7 on: July 03, 2021, 06:16:04 PM »
Okay, so at the appointment I took the tech with me to demonstrate the sound again. Was able to reproduce it so I don’t have to entertain that game. They scheduled an appointment for Monday to drop it off to have the axle torn down again. So I get my second rental in 20k miles. YAY. I’ll post aging once I find out any information. I did have them appraise the Jeep in case I wanted to trade when I get sick of the warranty game! I’ll let you guys know what they tell me.

Offline BLACKHAWKJEEP

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Re: Rotational rear end knock
« Reply #8 on: July 06, 2021, 07:40:58 AM »
Okay, so at the appointment I took the tech with me to demonstrate the sound again. Was able to reproduce it so I don’t have to entertain that game. They scheduled an appointment for Monday to drop it off to have the axle torn down again. So I get my second rental in 20k miles. YAY. I’ll post aging once I find out any information. I did have them appraise the Jeep in case I wanted to trade when I get sick of the warranty game! I’ll let you guys know what they tell me.

Thanks, definitely let us know what the outcome is! Good luck.

"... hey heim-joint, that's your name now!"

Offline TuffyMctuffy

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Re: Rotational rear end knock
« Reply #9 on: July 06, 2021, 10:06:50 AM »
Okay, so what they’re telling me is it’s an bearing issue. Bearings failing prematurely, so they’re replacing the bearing set again. I’m not really sure that’s the fix, but so far that’s all they’re willing to replace. It appears to be a bandaid fix, so I guess I’ll go along for the next 10k miles. If this happens a 3rd time, it should still be within warranty. So, if I end up here again next year, I’ll be ditching the brand. This makes two brand new Jeeps with annoying repeat issues. Thankfully warranty helps, but that doesn’t account for the aggravation of being at the dealer every year for a recurring problem.

Offline JustOnlyME

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Re: Rotational rear end knock
« Reply #10 on: July 06, 2021, 12:45:27 PM »
Bearing dont just prematurely go bad. The question is why are they going bad? Bad install? Something not machined correctly? Something bent?

Offline TuffyMctuffy

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Re: Rotational rear end knock
« Reply #11 on: July 06, 2021, 10:49:46 PM »
Bearing dont just prematurely go bad. The question is why are they going bad? Bad install? Something not machined correctly? Something bent?

I wish I knew the answer to that question. This first occurred at 9-10k miles and was so loud the first time, I thought the rear drive shaft came out of balance. They replaced all the bearings and it went away until I hit 21k miles. Now I’m back for the same issue. Albeit the sound is much more muted and not nearly as loud, it’s very distinct and easy to tell that it’s the same issue as before. For once I’d like to have a Jeep product that makes it to pay off without living at the dealer.

Offline TuffyMctuffy

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Re: Rotational rear end knock
« Reply #12 on: July 07, 2021, 01:10:19 PM »
OK, I just got off the phone with the dealer. They are telling me they are going to try rebuilding the entire rear axle this time, replacing all of the internal components instead of focusing solely on the bearings. I did ask if there was anything obvious, or potentially out of spec that would cause this premature failure as I do not want to be back for the same repair in another 10,000 miles. of course, I get the typical customer service line that they are working on trying to figure out the answers to my questions, but as of yet they do not have a definitive answer. So, it looks like I’ll be out of the jeep until minimum late next week waiting on parts and the actual repair. It does look like they noticed my rear windshield defrosters also fell off, so they’re taking care of that while it’s in the dealer. The funny thing is I was definitely expecting some Teething issues with the new 2 L turbo, but I was not expecting an axle problem at all.

Offline dave2002ti

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Re: Rotational rear end knock
« Reply #13 on: July 07, 2021, 02:14:24 PM »
Are they using a rear diff fluid with the proper additives for a LSD? Not sure if that can cause the bearings to fail but its worth checking into. The repair order from the reaplcement should have the fluid part number.

Lemon law and get a rubi with a locking diff rather than a LSD.


Dave Apker

Offline TuffyMctuffy

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Re: Rotational rear end knock
« Reply #14 on: July 07, 2021, 02:22:34 PM »
Are they using a rear diff fluid with the proper additives for a LSD? Not sure if that can cause the bearings to fail but its worth checking into. The repair order from the reaplcement should have the fluid part number.

Lemon law and get a rubi with a locking diff rather than a LSD.


Dave Apker

Yes, they are using the right fluid and the proper additives for the limited slip differential. Playing with the fluids and additives was the first attempt when the first repair was completed. It was part of their troubleshooting measures before ever opening the differential and inspecting the parts. As far as lemon law is concerned, the problems would have had to happen within the first 18 months of ownership according to DMV‘s website. It also requires the jeep to have been in the shop at least three times for the same repair within that time. I am only on my second repair for the same issue. If you know of any more precise information regarding Virginia’s lemon law, please include a link so I might research it myself. I may not even bother, considering this is my second new Jeep with recurring problems

 

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