Now as for the gearbox, as I mentioned in another thread I have been working on modifying it to run in reverse more reliably. At least I hope.
From what I can gather, the differential gear draws oil up and throws it into a little reservoir, where it then drips onto the jackshaft and I believe the helix direction then directs some oil into the bearing on the motor side of the box. Then, when the reservoir is full I believe the differential gear starts throwing oil between the bottom of the reservoir and the top of the jackshaft, where some of the oil that's travelling along the side walls is able to get to the back of the other gears via little pockets in the casting. Like so:
(Note the cavity above the reservoir is actually baffling for a vent. There is a matching cavity on the other half that allows air to pass through a labrynth and finally to a little breather hole that faces inside towards the motor for whatever reason.
So I figured I would install a scavenge pump that draws oil from the lower drain plug and feeds it back up to that top reservoir. Only problem is, the oil dripping through the single hole in the bottom only hits the jackshaft, and in reverse it wouldn't even be kicked in the right direction. So I set about adding some extra holes to the reservoir in the hopes that the oil will run down the side walls and into the same pockets in the casting. I also carved a small channel to try and help guide the oil even more. This was all done with a drill and a ball end mill on a dremel. Photos of this to follow later.
Then I had to add a port to get the oil into the reservoir. After some consideration I decided the best way in was through the side wall on the side opposite the motor. I stuck a neodymium magnet to the inside and outside to try and work out the best location to drill. It wasn't an exact science but it worked out. First I traced around the magnet, took it off and used the old eyecrometer to locate the exact center of the circle, then drilled a small hole to check that I'd be happy with its location on the inside. Hole location looked good, so I clamped it back on the mill, picked up the center again (this time with an actual center finder) and did a little spot face with a 3/4" end mill. Mainly I just wanted to nip off the edge of the fillet leading up to that mounting hole. I was pleasantly surprised to see the surface was also pretty parallel with the existing machined features.
Finally I drilled the hole and chamfered it. I didn't realize the casting was quite so thick here!
Finally, tap it 1/4 NPT using a spring loaded tap guide to keep it straight.
Side note, I read somewhere that if you stop a properly made tap with 6 threads still showing, you will have reached the correct depth. I checked this very tap against a proper thread gage once and it was bang on, so that's my goto rule of thumb from now on.
For the pump, I wanted to find something inexpensive but reliable, and with a current draw and flow rate far less than that of your typical transfer pump. I eventually found that certain BMW models used an electric pump to feed the oil cooler on either the engine, transmission, or both. They can be had cheap on eBay if you search for part number 11417834496 or terms like "M5 oil cooler pump".
This is what it looks like inside:
And if you carefully lift the tabs on the plastic housing, it can be pried off (there will be resistance due to an oring) and you are met with this:
Google that part number and you will find a nice datasheet stating it is rated for 2.81 amps continuous. Perfect.
So then I needed a mount for the pump since it has a flange and custom oring. I had to offset the holes a bit so I could use a 1/4 NPT outlet and 3/8 NPT inlet. Seemed to work out though.
And the mostly finished product. I will add mounting holes for it later once I figure out exactly how I want it.