Rear Differential Pinion Seal Leak

[blue_roster_cult]

I have a 2018 RWD Plat MAX with 231k miles (non-towing). I noticed a fluid puddle on the garage floor and found the pinion seal was leaking. The 9.75 3.31 rear end has never been serviced. I removed the driveshaft, pinion flange, and replaced the seal with Precision 4278 seal. The flange sealing surface is quite grooved, and probably should’ve been replaced. However, after two weeks of steady driving, no leaking has occurred. I marked everything and tightened the pinion nut to its original location. (This is not the recommended procedure) You can see in the pics that the original fluid looks clean, there was minimal metal on the plug magnet. I added nearly 2.5 quarts of motorcraft 75-85 and 4oz of friction modifier.

I will add that I ended up losing about 1/2 qt of lube within the 3-4 weeks between noticing the leak and getting to the repair.

 

[AWAR]

Everything you posted is similar to what I have witnessed with my former employers fleet of F150 pickups. Did you clean the magnet? If so you can monitor future buildup. We had very few wear problems unless they were abused. Over half were 9.75 with the rest being 8.8.

 

[blue_roster_cult]

Everything you posted is similar to what I have witnessed with my former employers fleet of F150 pickups. Did you clean the magnet? If so you can monitor future buildup. We had very few wear problems unless they were abused. Over half were 9.75 with the rest being 8.8.

Great! Yes, the magnet was cleaned