Mosey
Well-known member
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- #1
Hi all, I just completed a fluid service of the rear differential on my 2021 PB SCREW. My truck has 28k miles. This rear end, part of the max tow package, is sufficiently different from the traditional 9.75 that I thought some could use my experience to guide them. I had read and watched several how-tos on doing a diff service on a standard 9.75 diff.
To start, my differential had a metal gasket and o-ring. As shown in the photo, the o-ring is on the inside of the gasket.
This photo shows where the gasket/o-ring seals the differential on the cover. Note the large amount of corrosion that has formed outside of the o-ring.
Here is a photo of the differential housing. Another thing to note is the 3/4 floater DOES NOT have a sump like a standard 9.75. My truck is sitting level.
Cleanup of the surfaces took a while due to all the rust. The black is POR I used to coat the rusty axle. It proved to be most difficult to remove. I found two gouges in the cover left by the stamping process.
Once everything was clean and washed down with a copious amount of brake cleaner I was ready to put the cover back on. I used a Lube Locker gasket; It fit perfectly.
Lastly in a photo of the used fluid and new fluid. The fluid that came out was chocolate milk in color and opaque. The new oil is honey colored and translucent, just like motor oil.
To sum up, here are the things I noted.
To start, my differential had a metal gasket and o-ring. As shown in the photo, the o-ring is on the inside of the gasket.
This photo shows where the gasket/o-ring seals the differential on the cover. Note the large amount of corrosion that has formed outside of the o-ring.
Here is a photo of the differential housing. Another thing to note is the 3/4 floater DOES NOT have a sump like a standard 9.75. My truck is sitting level.
Cleanup of the surfaces took a while due to all the rust. The black is POR I used to coat the rusty axle. It proved to be most difficult to remove. I found two gouges in the cover left by the stamping process.
Once everything was clean and washed down with a copious amount of brake cleaner I was ready to put the cover back on. I used a Lube Locker gasket; It fit perfectly.
Lastly in a photo of the used fluid and new fluid. The fluid that came out was chocolate milk in color and opaque. The new oil is honey colored and translucent, just like motor oil.
To sum up, here are the things I noted.
- There is no RTV sealer, but instead a metal gasket with an o-ring.
- This was a lot of corrosion on the mating surfaces outside the area sealed by the o-ring.
- There is no internal sump.
- The only magnet I could find was the fill plug. It only had about 1mm of metal shavings (or paste) attached to it.
- It took 2.75 quarts of oil to refill the differential, including spillage.
- On a short bed truck the clearance between the diff cover and spare tire crash bar is very tight, I would estimate about 1/2 inch when the suspension is compressed. I am not sure any aftermarket cover, except the Ford Performance cover, would work. It is so tight I could not get my torque wrench and deep socket on the top-most bolt/stud.
- The use of a fluid extractor would probably be sufficient for most people. As long as mine does not leak that is what I will do next time.
- I plan on putting a bead of RTV around the cover to prevent further corrosion.
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