Gear Oil Pump

I recently needed to change the oil in the differential of my car, and unlike motor oil, you can just pour the new oil in from the top. The only way to get the oil in is to pump it in from under the car. Rather than buy a pump I quickly made one.

1. Empty Map/propane gas bottle
2. Bike inner tube valve
3. Map gas bottle lid
4. 1/4" ball valve
5. 1/4" brass coupling
6. Barbed hose joiner
7. Plastic Tubing
8. Thread seal tape
9. Solder
10. Map gas torch
11. Drill or lathe
12. Wirebrush or wirewheel on grinder
13. Large hole punch
14. Knife
15. Valve Remover
16. Paint (optional)

I used an old brass air coupler, but you can use whatever fittings you have on hand. You need to drill the hole out so it's large enough for one end of the barbed connector to fit into it.

You can do this with a standard drill, but I have a lathe, so I used that.

I used a small gas torch to heat up the brass parts and then applied the solder, it should wick itself into the joint and seal it up as well as keep the parts together.

Cut off the valve from an old bike inner tube and use a knife to remove as much of the rubber as possible. Before you can solder this into place, it needs to be perfectly clean. The easiest way to do this is to remove the valve from the stem with a removal tool. I then like to use the gas torch to burn the remaining rubber off, making sure to do this in a well-ventilated space.

Lastly, buff off the burnt rubber with a wirebrush or wirewheel; this should leave you with a clean brass surface.

To prepare the empty bottle, start by removing the valves with the same tool you used on the inner tube. Drill the valve hole on the side all the way through with a bit the same diameter as the bike valve stem.

Now you can drill the main hole through the bottle top. I like to start with a smaller bit and gradually work my way up through the sizes until the hole is big enough to receive the internal connector we made previously. Be sure not to go so large that the bottle's top comes off.

The bottle will likely have a lot of drill shavings inside that will need to be removed. Start by tipping it upside down and shaking everything out that you can. The inside needs to be clean, as you really don't want to pump metal shavings into your car's diff. If you have a small magnet on a stick, use that to pick up any particles left behind, then give it a good washout with water. I washed mine several times to be sure.

Remove the rubber seal from the screw-on lid and drill a hole through the centre of it, then insert the connector we made earlier and solder this into place.

Lastly, use a hole punch or a sharp knife to make the hole in the seal to the correct diameter to fit over the connector we just added to the lid.

Use the torch to solder the valve stem into place on the map gas bottle. Make sure there is no paint around this joint first, or the solder won't stick.

Once this has cooled back down, you can screw the valve back into the stem.

Cut a piece of the tubing so it reaches to the bottom of the bottle; cut the bottom on an angle. Now apply some thread sealing tape onto the other end and scew on the small ball valve. Lastly, apply more tape to the other side of the ball valve and screw on the final barbed connector.

Now you can push on the last part of the tubing on, cutting it to whatever length is appropriate for your needs.

Optionally, you can spray paint it so it looks nice.

For some reason, I can't get embedded YouTube videos to work right now, so here's the link until I figure it out.

https://www.youtube.com/watch?v=5tmuMNlrbj8

To use the pump, unscrew the lid and use a small funnel to pour the gear oil into the bottle (I'm only using kerosean for this test). It's important to not fill the bottle all the way; it needs to have space for the compressed air that will push the oil out.

Now screw the lid back on and use an air compressor or bike pump to pressurise the bottle. I've had mine up to 110 PSI with no issues.

Now insert the tube into the diff and slowly open the valve; the air pressure will push the oil into the diff.

In my video, you can see I opened it a bit too much, and the tube rocketed out. I left this here rather then edit it out to show what can happen if you don't hold it firmly. Also, using a thin liquid like kero flows a lot faster, oil flows at a more manageable speed.