I also have the rust and pitting on my truck rear axle. I went to the dealerships collsion repair and paint shop to ask what I should do to fix it. He first suggested Rustoleum but then recommended I ask a local auto supply store what to do. I though this was odd since they paint and do undercoating! The auto supply store salesman was quite helpful and recommended using a wire brush followed by painting with something called POR 15. The stuff cost about $10.00 including the brush and latex gloves. I put on the recommended 2 coats and it looks very good. Whether it will last or not is another question.

 

This has been a common problem with Ford vehicles across the board for years! I have a 2009 Mustang GT, purchased new in 08. NEVER seen salt, and only been caught in the rain twice since new! The rear diff looked like something out of someone's winter beater! On the stang, I wire brushed the heavier stuff off, and painted it first with rust oleum rusty metal primer, and followed with two coats of rustoleum satin black. Now looks brand new - like it should have when I bought it! On my 2011 F150, which I use as my daily driver, I coated the diff with Fluid Film, as I did with the entire undercarriage. I do a touch up once a year or so, and also coat the leaf springs to keep them quiet! Why Ford refuses to put a $1.98 coat of paint on these Diffs at the plant is beyond me! I guess they figure most people will never notice - or care. Apparently, I'm not the only one that does!

 

Read about my dealership experience in regards to this.

https://www.f150forum.com/f118/got-r...urself-296666/

 

Ford won't paint an axle or diff "at the plant" because they do nothing more than ASSEMBLE the drive train. If anyone were to "paint" it, it would be the supplier, and it wouldn't be "Ford" nor "at the plant".

 

Ford needs to keep the "Flex Fuel" stickers and paint our damn undercarriage.

 

My truck had this rust on the rear axle. Contacted my dealer, they got a hold of a Ford Engineer and my regional service manager. They cleaned it up and painted it. It looks great! We'll see how well it holds up before the rust comes back. Every '15 they had on their lot had this rust, so I would imagine Ford needs to do something about this...rust is a cancer once it starts, don't tell me it won't hurt anything...