Elektrik: Electric and transmission

[petoch]

Please HELP me. I can not speak German, so I decided to write in English. Sorry.
My problem:
I bought E32 730i (11/1989). There was a problem with automatic transmission. When I am trying to move in D, it will start moving with 2nd gear. After 10 - 15 meters there is 1st gear and it is still there until 6000 rpm and then tha transmission gives me the 4th gear - so I can drive a little bit faster. So there is no 3rd gear. It will come to 2nd gear, when I am driving around 20km/h. It is always the same even when I am trying to start with position 1 or 2 or 3. (except the 4th gear of course). In BMW they told me, that everything electric (control unit of transmission) is OK and there must be mechanical problem in transmission. So I bought another transmission with a control unit from a guy, who drove the transmission on a car (E32 730i 1987) from Germany to Czech republic. I changed the transmission and control unit. After starting the engine there was GETRIEBE PROGRAM. In BMW they told me, that there was one control unit until 9/88 and another one after 9/88. So I connected the original control unit and it was the same. So IT IS NOT MECHANICAL PROBLEM. Then they told me, that I need another control unit. I found the same one as I need - AND IT IS THE SAME.

PLEASE, let me know, how to check the cables from transmission to control unit if they are OK, where are all the connectors that need to be cleaned and what kind of sensors on engine are cooperating with control unit of transmission. I AM DESPRED. I THINK THAT I CAN FIND HELP HERE WITH YOU!!! I TRIED ALMOST EVERYTHING.

THANK YOU FOR YOUR ANSWERS.