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VKSheridan

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Did you look on the side? The rear isn't on the bottom but rather the side toward the rear.
How funny. THERE it is! I never noticed it like I did the front when I swapped the covers. Thanks!
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DanW

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How funny. THERE it is! I never noticed it like I did the front when I swapped the covers. Thanks!
They actually put it in the correct spot back there, protected from rock strikes! Glad you found it!
 

VKSheridan

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I've saved this epoxy in my Wish List, based on prior JL forum recommendations.
Before you seal it for life by potting it, there’s a chance the issue is not so much the conductance of an oil soaked PCB but possibly thermal/vibration micofractures at the soldering points (bad Chinese soak solder process).

LG TV’s are famous for their crappy motherboards dropping HDMI inputs. We’ve set the toaster oven to 450 F and baked the board to bring it back to life. Might need to do the same with the locker HET sensor but potting it will all but guarantee taking that option off the table.
 

wolf

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Jeep has tried to please both sides of the debate with my 2020 Rubicon JL:
Drain plug as pictured in the front differential
No drain plug (cover popper) in the rear differential
My 2020 has drain plugs front and rear. Great
 

CaJLMetalHead

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Before you seal it for life by potting it, there’s a chance the issue is not so much the conductance of an oil soaked PCB but possibly thermal/vibration micofractures at the soldering points (bad Chinese soak solder process).

LG TV’s are famous for their crappy motherboards dropping HDMI inputs. We’ve set the toaster oven to 450 F and baked the board to bring it back to life. Might need to do the same with the locker HET sensor but potting it will all but guarantee taking that option off the table.
I guess the issue would be that the PCB is enclosed in this plastic package that is sealed... I don't really see a way to remove the sealed top of the enclosure without damaging it..
 

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mgroeger

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I like the no drain plug. You can use the fluid evacuator to get it out. That way you don't break the cover seal. That's how I would change it if I didn't have the drain plug.
Yeah so that's not really a great idea. Plug or no plug the best way to change the diff fluid is to take the cover off. The reason is you can do a visual inspection of everything in there as well as taking some brake cleaner and giving it a squirt or two to clean off all the fine metal dust that clings inside there. The gaskets that come with the Jeep are extremely well designed and can be used multiple times, on one of my Jeeps I was up to 4 uses.

EDIT:
I would also check the SIDE of the diff at the bottom since the plug is most likely located there like it is on the rear diff of the Rubicon.
 
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VKSheridan

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I guess the issue would be that the PCB is enclosed in this plastic package that is sealed... I don't really see a way to remove the sealed top of the enclosure without damaging it..
I’ve read folks are drilling the PCB housing and filling it with RTV Silicone hoping to prevent failure. Various sources suggests oil entry via the wire connector is the most plausible location of entry. That makes sense since it appears the highest number of failures occur to those who disrupt the connector for whatever reason gear changes, rebearing, etc….

The problem with “fill and seal” is it’s a one way trip that won’t fix a cold solder joint.
 

No IFS

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I installed the Rancho front skid plate. It protects front drain plug nicely. It has a hole so I could still remove the plug for drainage without removing the skid plate. I it’s been working great for me.

62714834-0D50-410B-891F-009C1B5618BE.jpeg
 

Dyolfknip74

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I’ve read folks are drilling the PCB housing and filling it with RTV Silicone hoping to prevent failure. Various sources suggests oil entry via the wire connector is the most plausible location of entry. That makes sense since it appears the highest number of failures occur to those who disrupt the connector for whatever reason gear changes, rebearing, etc….

The problem with “fill and seal” is it’s a one way trip that won’t fix a cold solder joint.
It isn't RTV, it's specific potting material. And a ton of people had oil in the sensor without ever touching anything on their diff. Lastly, quite sure we haven't seen a potted one fail after the fact yet.
 

VKSheridan

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I’ve read the posts and yes, a dude used RTV. I can see how one might credit potting as the cure if they‘ve had no incidents after gluing a perfectly good board in place but is that the true cure or a miscredit? Not too sure.

There are several stories of “I potted it too late” which assumes the PCB components failed and not how they’re attached to the PCB. Once you pot it, baking the board becomes that much less likely to fix it.

I’m not trying to convince anyone they’re wrong, I’m just saying I’ve seen far more PCB’s fail from thermal/vibration micro-fractures then from being exposed to oil and other root causes could exist. If you want to resin your sensors, go for it, hope you get lucky.
 

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Dyolfknip74

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I’ve read the posts and yes, a dude used RTV. I can see how one might credit potting as the cure if they‘ve had no incidents after gluing a perfectly good board in place but is that the true cure or a miscredit? Not too sure.

There are several stories of “I potted it too late” which assumes the PCB components failed and not how they’re attached to the PCB. Once you pot it, baking the board becomes that much less likely to fix it.

I’m not trying to convince anyone they’re wrong, I’m just saying I’ve seen far more PCB’s fail from thermal/vibration micro-fractures then from being exposed to oil and other root causes could exist. If you want to resin your sensors, go for it, hope you get lucky.
The only way you can pot too late is if your rig is already showing a locker fault. Then the whole idea is moot.
Potted submerged sensors isn't something that was invented here on JLWranglerforum, it's a thing for a reason.
How many potted sensors have you seen fail? I don't mean these specific ones, just in general? I cant say I have seen any TBH, including about 20 years of military applications. It's literally done primarily to stop thermal and vibration issues.

Anyway, it's a cheap fix and if for some reason it actually does fail after the fact, I think you'd be hard pressed to find an FCA mechanic who would even see "the fix" therefore you'd just get a new axle under warranty anyway.

Your rig, do as you see fit. I personally think @chevymitchell did the community a great service with the walkthrough.
 

VKSheridan

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First and foremost, thank you for your military service. I totally understand the principles and usage of potting and yes, it’s nothing new.

Discussions in a forum can be difficult and I fear you’re missing my point. Read what you wrote…..

The only way you can pot too late is if your rig is already showing a locker fault. Then the whole idea is moot.
What I am saying is you can try to reflow (bake) the PCB before you conclude it junk. If continuity is lost or near lost due to an inadequate solder soak at time of manufacture, adding potting is unlikely to restore it.

Potting a sensor in advance *might* hold the components in place but it might not help if the component arc opens in its potted mount.

Opinion: I think the reason FCA wants to swap the whole axle is to increase the costs to Dana to make it unaffordable for them to restrict the sale of the sensors. Dana doesn’t want to sell the sensors? Fine, eat the cost of a bunch of axles……
 

chevymitchell

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First and foremost, thank you for your military service. I totally understand the principles and usage of potting and yes, it’s nothing new.

Discussions in a forum can be difficult and I fear you’re missing my point. Read what you wrote…..



What I am saying is you can try to reflow (bake) the PCB before you conclude it junk. If continuity is lost or near lost due to an inadequate solder soak at time of manufacture, adding potting is unlikely to restore it.

Potting a sensor in advance *might* hold the components in place but it might not help if the component arc opens in its potted mount.

Opinion: I think the reason FCA wants to swap the whole axle is to increase the costs to Dana to make it unaffordable for them to restrict the sale of the sensors. Dana doesn’t want to sell the sensors? Fine, eat the cost of a bunch of axles……
I think you're misunderstanding what's happening when the sensors fail. It's not cold/cracked joints.

They're failing because the gear oil has metal flake in it which is shorting out 1 of the 3 capacitors on the board. The potting material is just keeping the gear oil from getting to the PCB.

Nothing more than that.
 

Dyolfknip74

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First and foremost, thank you for your military service. I totally understand the principles and usage of potting and yes, it’s nothing new.

Discussions in a forum can be difficult and I fear you’re missing my point. Read what you wrote…..



What I am saying is you can try to reflow (bake) the PCB before you conclude it junk. If continuity is lost or near lost due to an inadequate solder soak at time of manufacture, adding potting is unlikely to restore it.

Potting a sensor in advance *might* hold the components in place but it might not help if the component arc opens in its potted mount.

Opinion: I think the reason FCA wants to swap the whole axle is to increase the costs to Dana to make it unaffordable for them to restrict the sale of the sensors. Dana doesn’t want to sell the sensors? Fine, eat the cost of a bunch of axles……
Lol, thank you. It was actually closer to a 30 years career, but I figured I would give the infantry a solid dozen years before I really knew what I wanted to do in the army, lol.

Tough to bake these PCBs though, the housing is destroyed if you try to pull out PCB.

Notwithstanding, I think @chevymitchell hit the nail on the head as to the cause of the failures.

Good discussion though, thank you.
 

VKSheridan

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I think you're misunderstanding what's happening when the sensors fail. It's not cold/cracked joints.

They're failing because the gear oil has metal flake in it which is shorting out 1 of the 3 capacitors on the board. The potting material is just keeping the gear oil from getting to the PCB.

Nothing more than that.
While it’s plausible microscoptic metal particles can migrate into openings in the sensor and short components, that is merely speculation used to affirm a preconceived failure mode. Arc surging a capacitor can create the same result.

Again, I don’t care if you guys want to pot everything on your ride, I’m just saying there is more than one way to fail a sensor and being oil soaked is not usually the primary failure mode.
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