Rust inside reax 8.8 axle

Good morning folks. I got a bit of good-news-and-REALLY-bad-news this weekend and need an outside perspective. First off, I would like to welcome Dolly to the family, shes a 1984 F150 regular cab with and inline 6, manual transmission, and a swapped 4X4... As implied by the song, Jolene (the 1985 F150 with the same specs) did not stand the test of time. Well in getting Dolly ready for registration, I need to reseal the axles and in cracking open the rear differential I drained the fluid and found a lot of rust inside.

At this point I should probably tell you that this truck had been swapped (by the previous, young owner) from a RWD to a 4X4.  When I opened up the pumpkin to release the axle shafts I was thrilled to learn I also had a factory limited slip on top of the 3.55 gear ratio; I was *not* so thrilled to see all the rust you'll see in the pictures below.

There was a ton of rust on the orbital (?) gear teeth and inside the tubes, but no apparent rust on the pinion. There was also a lot of rust settled on the bottom of tubes (where the axle shafts sit), on the actual axle shaft, and clinging to ceiling of the entire assembly. I cleaned as much as I could but was not really able to *completely* flush everything out of the tubes. I was able to get the separated rust off the teeth and what you see in the pictures is the resultant pock marking

So my question: Is this even worth trying to save? I'm worried about the rust particulates I that couldn't get out floating around in there tearing up the bearings. I suppose I could change the fluid every 500 miles until I feel better about it but that seems like a lot of work.

As luck would have it I have a separate 8.8 axle and am considering trying to install an aftermarket limited slip and 3.55 gears in that one and trading it over. But part of me likes the factory original

What Would Gary Do?

If there’s rust on the gear teeth then they are surely pitted and I wouldn’t use them.  But if they aren’t pitted that’s a different story.

I think I’d be inclined to do the aftermarket approach in the other axle.

Yes, sir. Those teeth are very pitted from the rust. I was able to get the rust off but the putting is very present. It's a shame too, this axle combo was such a nice little surprise to find.
Thanks for you input! sounds like I've got my work cut out for me.

I just overhauled an 8.8 like this last year. It was a "low mileage" junkyard purchase for a project, and it could have been sitting anywhere between 1 and 20+ years, I had no idea. I bought it online and had it shipped to me. It too was full of rust that had gotten through everything. However, the ring gear only had surface rust on the sides and back side, not on the teeth themselves.

The loose rust was everywhere, in the axle tubes, in the bearings, etc. I disassembled the axle and installed all new bearings and seals. Since I didn't change the ring and pinion, I didn't have to fool around with resetting the backlash, etc. I did check the pattern and it was fine.

One trick I did was I took a wire wheel that was about 1/2" larger than the ID of the axle tubes, and I welded a 1/4" rod to the end of it, about 3-4 feet long, and then used the drill to run this new long wire wheel back and forth through the axles tubes until they were shiny clean. Afterwards, clean with brake cleaner and push rags through the tubes.

Make sure the axle vent is clear and free. They do have a bad habit of getting plugged solid on the 8.8's.

In my opinion, the rust will ruin the bearings long before the ring and pinion. If it was all cleaned up with new bearings and oil, you'd be surprised at how long it would last;).