Front differential pinion seal leaking

[jatt143]

Just wanted to see if I'm the only one or if it's a widespread issue? I didn't see any other thread on this. it's with the dealer atm waiting on parts

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[jatt143]

Part # MB3Z-3254-A, if someone can help locate it or has an alternative?

 

[mike12779]

I am assuming I am having the same issue, just noticed it today. Time for a trip to the dealer.

 

[Ford Motor Company]

I am assuming I am having the same issue, just noticed it today. Time for a trip to the dealer.

Hello, Michael! Send us a private message with your VIN and the name and location of your local Ford dealer. I’d be happy to see what I can do to assist with this leak concern. Thanks!

 

[BroncoRick]

Just wanted to see if I'm the only one or if it's a widespread issue? I didn't see any other thread on this. it's with the dealer atm waiting on parts

I am having the pinion seal leak on the front diff as well. It's not a rapid leak, just a slow leak, but the dealer is saying that they have to replace the whole front axle.

Did you ever get yours fixed and how long did you end up waiting on parts? What did they replace for you?

 

[SPITmadFIRE]

I’m seeing this on my 2021 7MT just under 10k miles. Would love to hear from you other folks how it got resolved. Excuse the general wetness everywhere in the photos below — I did my oil change on a rainy day.

 

[jatt143]

Hey Guys, Sorry for the late response.

The only fix is to replace the Pinion seal and when I had my leak seal was about a 1month wait. luckily my local dealer found one but it still took them 2 weeks. here is the Part # MB3Z-3254-A you will be needing. once the part arrived It took only a few hours to remove and replace the seal and it was done under warranty.

 

[SPITmadFIRE]

Hey Guys, Sorry for the late response.

The only fix is to replace the Pinion seal and when I had my leak seal was about a 1month wait. luckily my local dealer found one but it still took them 2 weeks. here is the Part # MB3Z-3254-A you will be needing. once the part arrived It took only a few hours to remove and replace the seal and it was done under warranty.

Have you noticed any leaking afterwards? I’m a bit concerned about this issue happening more than once if they’re replacing it with the same part.

 

[jatt143]

no, around 6k miles on it after the repair. I just changed the oil last week and saw no leak

 

[BroncoRick]

I had this fixed this week. They replaced the entire front axle center section assembly. Seemed like overkill to me at first, but if there was anything wrong with the diff gears setup from the supplier of the original center section, which could plausibly lead to the early failure of the pinion seal, then it's the correct fix. A pinion seal should not fail within the first 10k miles... In 25 years I never had a pinion seal let go on my 4x4s, not even with high miles and lots of heavy use. It's a weird one and I would love to hear the true root cause, I'm sure Ford knows it by now internally.

 

[SPITmadFIRE]

This is all very reassuring, thanks for the updates! Please keep us posted if you notice any more leaks during oil changes.

 

[SPITmadFIRE]

… here is the Part # MB3Z-3254-A …

FYI it looks like there’s an updated revision for this part number, Tasca is showing it as MB3Z-3254-B:

https://www.tascaparts.com/oem-parts/ford-seal-assembly-oil-mb3z3254b

 

[SPITmadFIRE]

I had this fixed this week. They replaced the entire front axle center section assembly. Seemed like overkill to me at first, but if there was anything wrong with the diff gears setup from the supplier of the original center section, which could plausibly lead to the early failure of the pinion seal, then it's the correct fix. A pinion seal should not fail within the first 10k miles... In 25 years I never had a pinion seal let go on my 4x4s, not even with high miles and lots of heavy use. It's a weird one and I would love to hear the true root cause, I'm sure Ford knows it by now internally.

See above — looks like Ford has put out an updated seal revision without a TSB, which makes me worried less about the diff internals.

 

[BroncoRick]

See above — looks like Ford has put out an updated seal revision without a TSB, which makes me worried less about the diff internals.

It's definitely possible. My past experience with Jeep and Mopar parts was that often the part numbers will show a revision but nothing actually changed. Sometimes they just change them because of some supplier process that updates the revision for a reason other than a redesign.

My axle assembly was replaced with MB3Z4141C. That's the 4.7 geared locking diff / cast iron housing. The "B" of the similar part number is the 4.46 ratio. Both of these include the seal as part of the total assembly.

The seals could be leaking because they are not getting properly installed at the supplier (Dana, I believe). That could explain why some see the leak and others don't. If they fix this process over time then this issue would disappear for new owners, but it shouldn't require a seal redesign.

The seals could also be leaking because there is some issue with the pinion bearings / race or their installation in the housing, leading to some slight wobble in the pinion that over time (several thousands of miles) is leading to these leaks. The same could be true if there is some issue with the backlash adjustment or pinion preload. If that's the case, then replacement seals should also end up leaking, after some thousands of miles, when installed on the same diff housing.

If the design of the original seal was wrong then it seems like there should be greater prevalence of this issue, but maybe it's going unnoticed on many Broncos simply because it seems in a lot of cases, the leak in the seal is very slight. I wouldn't have noticed my own leak if I did not regularly climb under the truck to inspect it.

 

[SPITmadFIRE]

Dropped my Bronco off this morning for this front diff leak, as well as the 7MT TSB inspection. Fingers crossed they diagnose it as only the pinion seal and get parts ordered quickly.

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