Differential issues, is there a way for oil to leak from the engine into the front differential?

Tiny
RHANVEY
  • MEMBER
  • 2003 JEEP LIBERTY
  • 3.7L
  • V6
  • 4WD
  • AUTOMATIC
  • 170,000 MILES
Hi. Thanks for helping out. My general question is, is there a way for oil to leak from the engine into the front differential? I've never had to work on one.
For a little reference. I just finished up a bunch of work on the engine. Replaced a few pistons, heads, and various other parts. While test driving it, I noticed a sheering sound. Sounded like the front brakes were dragging. After removing the brakes to get everything resituated, I decided to spin the hubs just to make sure. I could hear noise sounding like when you used to put cards in your bike spokes lol. I removed each CV axle, 1 at a time and spun the other side. Noise was definitely coming from the diff. Then I noticed when I got underneath to guide the driver side shaft in, that engine oil was POURING out of the diff. I know it was oil from the engine because I had previously put uv for into the engine to trace down a leak. The oil that came out of the diff was clean with UV die in it. I'm extremely confused, as I swore the 2 were not connected. Unless the previous owner just happened to have done this right before I bought it. But that would be a 1 in a million coincidence. Sorry, this was so long. And thanks again.
Wednesday, January 22nd, 2025 AT 11:15 AM

3 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 49,440 POSTS
There is a vent tube to the front differential, if you have that connected to an oil cooler line then it will fill the front diff, can you please check that for me, it is the only way I can see that this would happen. Please upload pictures or videos in your response of any problems so we can see what to help you with.
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Thursday, January 23rd, 2025 AT 12:05 PM
Tiny
RHANVEY
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Sorry it took so long to respond. So, I checked the vent tube, and it just runs up and is attached a clip on the motor mount. I guess I'm going to chalk it up to previous owners, since this makes no sense at all lol. About the noise in the differential. I was told by another mechanic to check the intermediate shaft inside the diff. Problem with that, if it is the problem, I can't seem to find a replacement for it anywhere. Also, I'd really prefer not to open it up and start testing everything inside. If it comes to that, I think I'll just swap the whole thing. Is it possible that the noise was being caused by the fact that there was engine oil in it instead of gear oil? Do u think it's worth my time to drain it and replace the oil? The CV axles are currently still off the car. So, if you don't think the oil swap will work, again, I'll just swap the whole diff. That way I'm not putting it all back together just to take it apart again. Thanks again for your help.
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Sunday, January 26th, 2025 AT 10:57 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 49,440 POSTS
Yep, you are correct, if the CV axles are off and it still makes the noise I would swap the diff out. It sounds like one of the carrier bearings is no good. Here is how the job is done. Check out the images (below). Let us know if you need anything else.
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Monday, January 27th, 2025 AT 9:22 AM

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