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Rear Diff CV Shaft Seal

RichCresci

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Hello friends,

A few months ago I purchased a new to me 2006 Mountaineer AWD 4.0 with 128,000 miles. When I purchased it, I noticed the left rear cv shaft was newish. About 3,000 miles later and after a 100 mile highway drive, I noticed the rear differential cv seal had let go on the newish axle. As it is my daily driver I went to my local Autozone and bought a new seal. When I replaced it, I noticed the new seal was no where near as hefty as the factory one and it had appeared as though someone tried to remove the old seal and failed. I didn't think much of it, did the job, refilled the diff with 75-140 gear oil and went on my way. Its been leak free for about two weeks and 500 miles. Today, I noticed the seal I replaced is dripping for the first time since installation. It's only leaking from the lower 1/4 of the seal though (from 5 o'clock to 7 o'clock).I should note that its 97 degrees out, but either way, it shouldn't leak. I checked the breather and it seems to be working fine. also, the 130,000 mile and 13 year old passenger side seal is holding strong.

Does anyone have any experience with Autozone seals? Is the motorcraft one any better? The bearing in the axle seems tight as can be, I just find it hard to believe that the new seal isn't doing its job. I also find it strange how its only leaking from the bottom, if it were the bearing I feel like it would leak from all over.

Any insight would be greatly appreciated. Thank you
 



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MotorCityFats13

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service parts are never the same quality as the true oem part and even if you bought the motorcraft part it would also be a service part there are only so many manufacturing facilities sometimes they all just get pushed out of one build house and branded

its possible the seal got pinched when you put the shaft in and all that is needed is to pull it out and in a few times
 






RichCresci

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I swapped the Duralast seal for a Motorcraft today. The two seals can’t even be compared. The ford seal was MUCH tighter on the axle and took a lot more effort to seat into the diff. The Duralast seal popped right out with a screwdriver.

I would advise anyone doing this job to only buy the Motorcraft seal. Don’t waste your time with aftermarket
E3691DD0-7346-4F3C-885A-A34166BD2C8F.jpeg
4A3F3BF2-383A-4665-971C-248C2E78BA17.jpeg
BECA73CC-6C7F-43D9-A9D7-2C4EEEDD0155.jpeg
E8514A59-4E11-44AD-9F9E-21C001DE02D0.jpeg
 


















RichCresci

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First and last pic are Motorcraft, middle two are Duralast.

You say you have dirt on top of the cv axle shaft?
The cv shafts turn, typically when dirt sticks to them it means they’re leaking. Earlier gear oil from the diff or grease from the cv shaft.
 


















96eb96

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Ford improved the design so you don't need a tool to install it and protect the seal. The aftermarket may not have caught on.
I also read a TSB that some leaking may be OK after it is installed, as long as it goes away. The seal works out some trapped fluid.
 






imp

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First and last pic are Motorcraft, middle two are Duralast.

You say you have dirt on top of the cv axle shaft?
The cv shafts turn, typically when dirt sticks to them it means they’re leaking. Earlier gear oil from the diff or grease from the cv shaft.
@RichCresci

Seals can also leak around their OD (Outside Diameter). This leakage is quite difficult to not vthinkn it originates from the seal rubber element. The brown shi* in the images is aimed at positively sealing the OD with, like, an O-ring. Usually means a quality seal.
 






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