KNOWN ISSUE? Rear end clunking on take off and switching into reverse (2020 JTR-automatic)

[545moose]

I've noticed it occasionally and its subtle but there enough to be annoying and on my mind. It reminds me of the recall on the driveshafts Toyota had on FJ cruisers which felt the same way. Not ever having a Jeep I thought I'd check in here first before bothering the stealership again, but I'm under warranty still, just don't want to do the drop off/carless a day/pickup shuffle unless there could legitimately be something wrong. TIA.

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[jbehrn]

I’ve got a 22 Rubi and it makes a popping sound due to a brake check when I take off. No clunking sounds though…

 

[JAVIERGONZO]

Does it jerk a bit when you put it in reverse

 

[jac04]

Both my 21 Mojave and 14 JK Rubicon make the same rear clunk on transition. Most of the time it is fairly subtle, but sometimes when shifting from R to D or D to R, it is quite noticeable. Both have the factory ELD which is made by GKN. If you look at the way the GKN e-locker is made, it is my understanding that the spider gears & side gears are made with a significant amount of play (backlash) to allow for quicker/easier engagement of the dog clutch teeth when you select the 'lock' function. There is also quite a bit of play between the 4 legs of the outboard dog clutch and the diff carrier.

The clunk you are hearing is mostly the engagement of the spider & side gears as they take up the play. There could also be a clunk from the 4 legs of the dog clutch contacting the differential carrier.

BTW, I have actually had 2 different rear axles in my JK, both with the factory GKN locker, and they have both made the exact same noise.

If you are interested in seeing what one of these GKN lockers looks like and how it works, check this out:
https://www.jkowners.com/threads/oem-rubicon-locker-study.88678/

 

[545moose]

Both my 21 Mojave and 14 JK Rubicon make the same rear clunk on transition. Most of the time it is fairly subtle, but sometimes when shifting from R to D or D to R, it is quite noticeable. Both have the factory ELD which is made by GKN. If you look at the way the GKN e-locker is made, it is my understanding that the spider gears & side gears are made with a significant amount of play (backlash) to allow for quicker/easier engagement of the dog clutch teeth when you select the 'lock' function. There is also quite a bit of play between the 4 legs of the outboard dog clutch and the diff carrier.

The clunk you are hearing is mostly the engagement of the spider & side gears as they take up the play. There could also be a clunk from the 4 legs of the dog clutch contacting the differential carrier.

BTW, I have actually had 2 different rear axles in my JK, both with the factory GKN locker, and they have both made the exact same noise.

If you are interested in seeing what one of these GKN lockers looks like and how it works, check this out:
https://www.jkowners.com/threads/oem-rubicon-locker-study.88678/

Great info, thanks a ton man! Glad to hear it’s consistent at least.

 

[Glad_he_ate]

There is also play side to side in your drive shaft via the carrier barring. It’s in a floating/ rubber isolation housing and a keen owner may notice the shift in pressure from one side of the housing to the other as the drive shaft switches directions.

 

[Rocksalt]

my 2020 Soort S does it... as did my 2016 JK.. mostly when on ani incline shifting from Park to reverse... seems like typical slop to me but if had any shifting issues while driving then i would get it checked .

 

[adampwilliams]

Both my 21 Mojave and 14 JK Rubicon make the same rear clunk on transition. Most of the time it is fairly subtle, but sometimes when shifting from R to D or D to R, it is quite noticeable. Both have the factory ELD which is made by GKN. If you look at the way the GKN e-locker is made, it is my understanding that the spider gears & side gears are made with a significant amount of play (backlash) to allow for quicker/easier engagement of the dog clutch teeth when you select the 'lock' function. There is also quite a bit of play between the 4 legs of the outboard dog clutch and the diff carrier.

The clunk you are hearing is mostly the engagement of the spider & side gears as they take up the play. There could also be a clunk from the 4 legs of the dog clutch contacting the differential carrier.

BTW, I have actually had 2 different rear axles in my JK, both with the factory GKN locker, and they have both made the exact same noise.

If you are interested in seeing what one of these GKN lockers looks like and how it works, check this out:
https://www.jkowners.com/threads/oem-rubicon-locker-study.88678/

What doesn't make sense is if they are all built with the same ELD made by GKN, you should have every single jeep should make that noise. Do the JL rubicon's have the same ELD from GKN? I've driven a friends JL to see if it does it, and it's smooth as butter on it's automatic down shifts.

 

[jac04]

As far as I know, the JK and JT/JL lockers are the same basic design, but not the exact same parts due to the change over to the Advantek axles.

I've never noticed it on either downshifts or upshifts - both my JK and JT are autos. You can typically get it to make the sound by transitioning quickly on & off the throttle when going slowly in a low gear. You can also hear it sometimes when transitioning between R and D, or putting it into gear from P. It is a subtle clunk - it's not like you hear it and think something is really wrong.

 

[DocMike]

Did you put on a lift?
I find checking torque on all my suspension components every few months helps cut down on the noises. Especially after a rather robust off road session.

 

[adampwilliams]

Yeah, all that's been checked. The clunk was happening from stock, though.

 

[DBravo]

I've noticed it occasionally and its subtle but there enough to be annoying and on my mind. It reminds me of the recall on the driveshafts Toyota had on FJ cruisers which felt the same way. Not ever having a Jeep I thought I'd check in here first before bothering the stealership again, but I'm under warranty still, just don't want to do the drop off/carless a day/pickup shuffle unless there could legitimately be something wrong. TIA.

I have this as well in my '20 Gladiator JT Overland. I've noticed it is less likely to happen if I step down hard on the brake when i shift in to gear. It also happens occasionally if you let off the gas to coast and then immediately touch the pedal again. Also if taking off from a complete stop and the truck has rolled back slightly. Engaging the Hill Start Assist seems to keep it from happening when stopped on an incline .
I'm at 52k and it has remained consistent, has not changed in tone or conditions when it occurs and my diff fluid is normal/not discolored and no visible metal.
I'm inclined to agree with the assessment provided by jac04 related to play in the diff.

 

[jeepers29]

I get a clunk when I step on the brake going forward, then will not get another until I have used the brakes going in reverse, where I get a clunk. One clunk until using brakes in oppisite direction. I have checked everything and can't find anything loose. Bringing to the dealer for recall flash and they can look for it.

 

[545moose]

I get a clunk when I step on the brake going forward, then will not get another until I have used the brakes going in reverse, where I get a clunk. One clunk until using brakes in oppisite direction. I have checked everything and can't find anything loose. Bringing to the dealer for recall flash and they can look for it.

Good call and angle to take.

I'm going to ask about it when I go back in soon for an oil consumption verification; somehow my 3.6 ate 1.5 qts. in 1200mi and no sigh of it anywhere externally, so... they're working towards a new motor if so. So more to come there obviously :/ Oh and I have rust on my tailgate lip on the bottom edge and bubbling in spots, so add that. deep breaths here, 1, 2, 3.....

 

[jeepers29]

Good call and angle to take.

I'm going to ask about it when I go back in soon for an oil consumption verification; somehow my 3.6 ate 1.5 qts. in 1200mi and no sigh of it anywhere externally, so... they're working towards a new motor if so. So more to come there obviously :/ Oh and I have rust on my tailgate lip on the bottom edge and bubbling in spots, so add that. deep breaths here, 1, 2, 3.....

Good luck with the new engine. I am surprisd that they didn't tell you that was normal consumption.

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