Today I did the rust repair and final painting of the differential. The first thing I did was to give it a quick final cleaning using Simple Green to remove and grease on the surface from handling and working with the differential case since I last cleaned it. Prior to introducing and water I replaced the fill and drain plugs, the breather, and taped off the axle openings to keep water from getting inside.
Before painting I used an acid etch to brighten up the aluminum front of the differential. I used an Eagle One Mag Cleaner which is designed for rough-finish aluminum wheels. I donned my safety glasses and heavy rubber gloves (this is acid, after all) and sprayed the aluminum liberally.
Per the instructions, I waited thirty seconds while the acid did its etching on the aluminum, which caused a fairly vigorous foaming.
Then I washed it off very thoroughly with water.
Then I turned my attention to the rest of the differential. The case itself had several rough areas where the original paint had worn off and surface rust had set in. I had previously used a wire brush to remove and loose material. Before painting, I sealed the remaining rusty areas using Eastwood’s Rust Encapsulator product, which is supposed to seal in rust and neutralize its ability to deteriorate any further. I bought a quart can for $19 and applied it using a regular paintbrush.
There was a lot of rust around the edges of the axles, presumably from the finish being chipped by rocks and stones kicked-up by the tires. I painted over all of those areas with the encapsulator.
There was also surface rust around the welds at the rear of the “pumpkin,” which I painted over.
I rotated the differential to point down so I could access the areas underneath, and completed sealing over all of the rust areas.
After allowing the Rust Encapsulator to dry for four hours, as recommended by the instructions on the can, I prepared for the finish coat of paint. I masked off the aluminum part using heavy-duty foil and some painter’s masking tape. You can tell Thanksgiving is on my mind already!
Then I removed the plugs. The paint I used is Eastwood’s aerosol Chassis Black, which was $13 for the can.
I applied two coats, waiting 20 minutes between coats.
Then I rotated the differential up again in order to apply two coats to the areas I had missed.
After allowing the paint to try for several hours, I moved the differential into the garage to dry over night. I removed the masking from the aluminum area.
Overall I’m pleased with the results, particularly compared to the way it looked when I pulled it off the car.