Here's an article that shows a tranny service on a 4hp22. Hopefully you can identify it.
http://www.pelicanparts.com/BMW/tech...Fluid_Auto.htm
That fact that you have a fill tube makes me almost sure it is a 4hp22. There is a metal tag on the driver side, near the pressure taps, but I'm sure you checked that. You can use the tube for the dipstick to add a little. Otherwise the drain/fill plugs on the sump.