TO whom it may be addressed: I am tryingto get some iformation o the ZF transmission used by BMW. Is it true that durig the 80's they used only one type of ZF/3HP-22 transmissio for all 3, 5, 6, and 7 models? If they are the same,are they interchangeable? I am aware that the newer models have 4 speeds but is it i the same case or is the overall length longer? If anyone has a cross reference specification, I would appreciate your help