2012 5.7l hemi Front diff leak...not sure of the cause

[SalvageRam]

My 2012 Ram 1500 5.7 liter Hemi has a front differential leak, and I need help pinpointing where exactly it's coming from. In the pictures provided, you can see that there is a small and slow leak on the front diff where it connects to this second half of the front diff. Not sure what its called exactly:


Just by smelling it I can tell its gear oil. Has that sulfur like smell. I ran my hands all along the top of the differential, and there's no gear oil leaking from there, just dust. Also, where the driveshaft connects to the front diff is dry, as you can see in this picture.


The previous images are from if you were looking at the diff from the rear of the truck. Here are some images from the front just to show that the fill plug, the drain plug, and the areas around it are also dry.


My best guess is that where these two parts of the diff meet, there may be a part of the gasket that's failing. Here's an image of some excess gasket material that was squeezed out when it was first installed. It does feel slightly moist in this area.
Back:

Front:


Here are some conditions that I've been able to figure out. This seems to happen after the car has been driven for a little bit. Usually if I drive it around the block a couple of times and I come back to the garage, there will be a drop or two under the diff. This does not happen just when the car is started and in park. It happens after it's been driven. If I leave the car in drive or reverse while stationary, the leak does not happen. The leak is slow and a few drops. I have not tested putting it in four-wheel drive yet. But if anyone thinks that's necessary to do, I'll try it out.
So my questions are, where is this leak coming from? Has anyone on this forums seen this type of leak before? If it is what I think it is, how involved is repairing it? The rear diff is pretty straightforward in that you just take off the cover, clean and reseal. But the front diff isn't as straightforward. Any and all help is greatly appreciated.

 

[SalvageRam]

this is pretty interesting. I sent this thread link to ChatGPT and this is what it responded with. What do ya'll think?

ChatGPT Response:

Likely diagnosis​

The leak is most likely coming from the RTV-sealed joint between the main differential housing and the passenger-side axle-tube/disconnect housing.


The wet area follows that vertical mating seam, with oil collecting at its lowest point. The pinion seal, fill plug, drain plug and upper housing appear dry in the supplied photos.


The “second half” identified in the post is called the axle tube assembly in the factory service information. It contains the output shaft and front-axle disconnect mechanism. The black component attached to it is the disconnect actuator housing.


This joint does not use a conventional paper gasket. The factory procedure specifies a 1.5 mm bead of Mopar silicone RTV or equivalent on both mating surfaces. It explicitly warns that incorrect RTV application or waiting more than three to five minutes before assembly will cause a leak.


Visible RTV squeeze-out by itself is normal. The wet trail along the seam is the stronger evidence that the seal has failed.

Why it leaks only after driving​

That behavior fits a housing-seam leak:

• Wheel movement rotates components inside the front axle even when the truck is not actively driving the front wheels.
• The gear oil gets splashed against the housing and becomes warmer and thinner.
• Sitting stationary in Drive or Reverse does not rotate the wheels or axle components, so little oil reaches the failed portion of the seam.

Testing four-wheel drive is not necessary to diagnose this. It could make the leak more noticeable, but the fluid level should be checked before any further driving or 4WD testing.

Other possibilities to eliminate first​

Before disassembling it:

1. Degrease the entire housing and seam with brake cleaner and dry it completely.
2. Apply talcum powder or leak-detection powder across the seam, then drive briefly and inspect the first wet location.
3. Check the differential vent hose and cap for kinks, mud or blockage. A blocked vent can increase internal pressure and force oil through the weakest seal.
4. Remove the fill plug and verify the fluid is still approximately level with the bottom of the fill opening.
5. Inspect the passenger-side output/axle seal. A leaking shaft seal can sometimes allow oil to migrate along the casting, although the photos point more strongly toward the housing seam.

Repair involvement​

This is more involved than resealing a rear differential cover, but it is not necessarily a differential rebuild. The ring gear, pinion depth and carrier adjustments are not disturbed when only the axle-tube joint is resealed.


The factory sequence is essentially:

• Remove the passenger-side CV halfshaft.
• Remove the shaft snap ring, O-ring and oil slinger.
• Unplug and remove the axle-disconnect actuator.
• Remove the axle-tube assembly bolts.
• Separate the axle-tube assembly from the differential housing.
• Completely remove the old RTV and degrease both aluminum mating surfaces.
• Apply a 1.5 mm RTV bead to both surfaces.
• Assemble within three to five minutes.
• Torque the axle-tube bolts to 65 N·m / 48 ft-lb.
• Reinstall the actuator, using a new actuator gasket if needed, and torque its bolts to 27 N·m / 20 ft-lb.
• Install a new axle seal, oil slinger, O-ring and retaining ring as specified.
• Refill and verify the differential-fluid level.

My assessment from the photos is high confidence that this is the axle-tube-to-differential-housing RTV seam, but the clean-and-powder test should confirm the exact starting point before parts are removed.

 

[DILLIGAF]

I didnt read any of that ai garbage,

Dropping the front diff isnt hard, Just need to pull the CVs and only a couple bolts hold up the diff.

Split the case and reseal it.

 

[SalvageRam]

haha completely understand. The AI also said the seal between the main housing and axel tube which is what i was thinking it was but just not sure of. I've never resealed a diff but i have resealed oil pans so figure it's the same process when applying RTV.
Are you fairly confident that's the issue?
I'm thinking i may not need to drop the diff. If i can just remove the passenger side CV axle then take out the axle tube and clean and reseal? at least thats what the AI seems to imply.

 

[mdc1990zr1]

haha completely understand. The AI also said the seal between the main housing and axel tube which is what i was thinking it was but just not sure of. I've never resealed a diff but i have resealed oil pans so figure it's the same process when applying RTV.
Are you fairly confident that's the issue?
I'm thinking i may not need to drop the diff. If i can just remove the passenger side CV axle then take out the axle tube and clean and reseal? at least thats what the AI seems to imply.

You can clean the area real good, add some UV dye. Drive it to heat it up and check it with the UV light. I don’t believe the cost a whole lot, had mine for decades. You might be able to rent it from a local auto parts store

 

[Daw14]

Jeez man ,just flex-seal it .
No need to get all technical.

 

[jws123]

That is such a small leak for a 2012 my lazy ass would just check the fluid every other oil change lol but yea if it bothers you just re seal it.

 

[SalvageRam]

You can clean the area real good, add some UV dye. Drive it to heat it up and check it with the UV light. I don’t believe the cost a whole lot, had mine for decades. You might be able to rent it from a local auto parts store

Not a bad idea. I should have some dye somewhere in my garage. I'm going to also double check the vent tube that connects to the diff. I saw some posts that mentioned that could get clogged.

 

[SalvageRam]

That is such a small leak for a 2012 my lazy ass would just check the fluid every other oil change lol but yea if it bothers you just re seal it.

Normally this wouldn't bother me too much but this was a salvage auction truck and I'm going to be scheduling and inspection soon to get the rebuilt title. Just don't know how tedious MI is with their rebuilt inspections. Some say its easy, some say they could fail you for small things. The internet is very inconsistent lol

 

[SalvageRam]

Holy crap, I think i hit the lottery fellas! So I checked out the front diff breather tube and couldn't blow any air out of it. Unless I strained really hard then a little air came out but I don't think it should be that difficult. Did a test drive with it off and no leak! I'm going to keep an eye on it and we'll see if it leaks after extensive driving but i did the same drive as last time and no leak!! I will be ordering a new one

 

[Daw14]

Holy crap, I think i hit the lottery fellas! So I checked out the front diff breather tube and couldn't blow any air out of it. Unless I strained really hard then a little air came out but I don't think it should be that difficult. Did a test drive with it off and no leak! I'm going to keep an eye on it and we'll see if it leaks after extensive driving but i did the same drive as last time and no leak!! I will be ordering a new one

Cool beans on finding the cause , and thanks for sharing.

 

[EdGs]

 

[Dodge 1500 4X4]

There is a check valve in that tube, probable clogged, so water or Debree can't get into the housing maybe you can just clean it out.

 

[TRX571]

Hi, I have exactly the same problem with my 2022 TRX! How has your truck been since you fixed the breather issue by temporarily removing the check valve? Has the problem stayed away?