Rear Diff Leak?

[shoenough]

Hello,

Something is leaking towards the middle/rear of my 2014 SHO PP. It is black, greasy, and drier than motor oil. I don't have ramps and haven't had a good look underneath to determine the source but the area has to be around or near the rear differential. Is a rear diff leak common? Could it possibly be the PTU vent?

I've noticed a very light/faint hum noise coming from the rear when driving - especially around the 40MPH mark. It could be normal but figured it was worth mentioning - maybe related?

I'm hesitant to take it to the dealer but it is under the CPO warranty. I'll be livid if I pay the $50 deductible to be told "it's normal". My experience with warranty claims with any dealer has never been great.

 

[krewat]

Definitely get it checked by the dealer, especially with the noise you describe. Sounds like the thing is getting ready to grenade.

 

[SHOdded]

X2, Probably need a new RDU.

 

[ctrlraven]

The other month ago I noticed two quarter size spots in my garage, got under the car and saw the rear diff cover and the exhaust was wet from fluid. Found there was a TSB about the diff vent cap in cold weather. Took it to the dealer along with the TSB printout and confirmed the diff had vented a fair amount of fluid out. Dealer covered it under the 5yr/60k mi powertrain warranty on my 13 MKS.

Here is the TSB

TSB 14-0057 (supersedes TSB 12-8-12)

ALL WHEEL DRIVE – FLUID LEAK FROM REARDIFFERENTIAL VENT CAP – TEMPERATURES BELOW 0 DEGREES C (32 DEGREES F)

Publication Date: March 14, 2014

FORD: 2011 Taurus; 2011-2012 Escape, Fusion; 2011-2013 Edge, Flex; 2011-2014 Explorer, Taurus
LINCOLN: 2011-2012 MKZ; 2011-2013 MKT, MKX; 2011-2014 MKS
MERCURY: 2011 Mariner, Milan

This article supersedes TSB 12-8-12 to update the vehicle model years.

ISSUE:

Some 2011 Mariner, Milan, 2011-2014 Taurus, Explorer, MKS, 2011-2013 Edge, MKX, 2011-2012 Fusion, MKZ, 2011-2012 Flex, MKT, 2013 Flex and MKT vehicles equipped with a 3.5L GTDI engine may exhibit an occasional fluid leak coming from the rear differential vent cap in temperatures below 32 degrees Fahrenheit (0 degrees Celsius) under certain conditions.

ACTION:

Follow the Service Procedure steps to correct the condition.

SERVICE PROCEDURE
1.Inspect the rear drive unit for oil leaking from the reardifferential vent cap located on the rear cover.
a.If only a light residue is found around the cap, this is normal. This article does not apply.
2.Remove and discard the rear differential vent cap from the rear drive unit cover.
3.Install a new rear differential vent cap.
4.Clean off any remaining residue.

PART NUMBER PART NAME
DB5Z-4022-A Differential Vent Cap

OPERATION DESCRIPTION TIME

140057A 2011 Milan, Mariner, 2011-2012 Escape, MKZ, Fusion, 2011-2014 Taurus, MKS 2011-2013 Edge, MKX: Inspect And Replace The Rear Drive Unit Vent (Do Not Use With Any Other Labor Operations) 0.3 Hr.
140057A 2011-2014 Explorer, 2011-2013 MKT And Flex: Inspect And Replace The Rear Drive Unit Vent (Do Not Use With Any Other Labor Operations) 0.4 Hr.

WARRANTY STATUS

Eligible Under Provisions Of New Vehicle Limited Warranty Coverage.
Warranty/ESP coverage limits/policies/prior approvals are not altered by a TSB. Warranty/ESP coverage limits are determined by the identified causal part and verified using the OASIS part coverage tool.

DEALER CODING

 

[shoenough]

I've looked at this a little more since my original post. It is definitely coming more from the middle than the rear so I don't think it's going to be the rear diff. It's about 8' back from the front, near the middle width wise, and does not appear to be hitting the exhaust from what I can see. Where is the PTU vent located?

I don't have ramps or a jack and stands so I can't get under it to figure it out. I also can't seem to find any good pics or complete diagrams of the underbody that would help narrow it down. Everything looked clean looking underneath from ground level without being under it (didn't see anything on the exhaust). It does not constantly leak - I moved it to the driveway for over 8 hours yesterday and nothing leaked.

I'm attaching a pic for reference. I'm going to take it to the dealer under the CPO warranty but I always like to have an idea of what it could be before I go in when possible.

 

[ctrlraven]

If your cpo is still in the 12 month/12k mi comprehensive warranty, definitely take it in cause it will cost you nothing. If it isn't then your still covered but pay your deductible if something is wrong. Show that picture to your service writer when you take it in also.

 

[SHOdded]

could be the rear PTU seal (PTU to driveshaft). Should be visible with good light. The driveshaft itself could be at fault, but does not seem like it from your description. That is typically accompanied by vibration through the floorboards.

 

[shoenough]

Update: I'm glad I took it in for service. Right hand halfshaft is ***** (covered under recall) and the leak is oil coming from the valve cover. So two issues discovered.

I'm a little concerned about the oil leak from the valve cover at such low mileage (40k)...a quick search here indicates it might not be uncommon. Any thoughts on that?

 

[SHOdded]

Rare to have a VC leak again after it is fixed at the dealer, in fact, I am hard pressed to remember a single case of recurrence.

 

[ticoscen]

Rear RDU is a separate unit from the front PTU. PTU is a geared mechanism. The RDU is the differential which also has an electronic clutch mechanism controlled by the ECU. Different oil for the front PTU: 175W. Rear / "RDU" used 90W and holds more. Transmission fluid for the the tranny is LV Mercon. So, 3 area's need **** and attention for transmission related stuff. 1. Tranny. 2. PTU 3. RDU Adding a drain plug to the PTU and RDU will make drain and fill easy and quicker. I used two 1/8-27 St. steel magnetic pipe plugs. Got the TAP and DRILL on Amazon too. Drill and Tap: https://www.amazon.com/GlowShift-NP...48ab8&pd_rd_wg=l4UZT&pd_rd_i=B00CA91AIK&psc=1

PLUG:
https://www.amazon.com/gp/product/B002A378M8/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1