http://www.awdwiki.com/en/bmw/Tsiteeri:
5-Series E34 525iX 1991-1996
Full-time all wheel drive. Torque split 36% front / 64% rear. Computer controlled system using the ABS sensors to detect wheel slip.
The E34 system exists in 2 generations with a major difference:
Generation 1 has separate control unit which control electromagnetic semi-wet multiplate disk clutch in centre and electrohydraulic wet rear differential. It recieves ABS wheel sensors data signals from special, modified ABS unit. Front differential open. In production from april 1991 up to september 1993.
Generation 2 has ABS/ASC+T unit which controls semi-wet electromagnetic multiplate disk clutch in centre and an open differential rear through rear wheels brakes (ABD). It also controls throttle. Front differential open. In production from October 1993 up to end of production.
Most components looks very similar to 325ix E30 models but are unique parts.