Flex Disk Coupling (archive)

The factory service manual shows that two versions exist for the 1991 850, one with what your're calling a Hardy disc, commonly called a Joint Disk, Flex Disk or Guibo. The other has a half-moon shaped coupling with only a universal joint(you referred to as a Polheim joint?).

If you have to replace either, I'd suggest using one of the driveshaft refurbushment places listed in Roundell (One in Sacramento, Ca and another in Portland Oregon). If a universal joint is bad, they can replace joints and rebalance the shaft for $300 for 2 universal units, and $340 for 3. Much less than BMW and same or better quality. The Flex Disk coupling and Center support bearing are extra. Get OEM from an aftermarket like Zygmunt Motors and they are relatively cheap pieces (about $35 for the center bearing).

: Strange.. no Hardy disc on my 850i! So first, is it a 850i? My frind had to chnge the Hardy disc on his M5, so thet was one of the first things i checked when i got my 850, but there is just a normal Polhem joint(i think that's what they are called? same type as on any american car). The Hardy disc should be a black rubber piece where the driveshaft connects to the gearbox.

: Sam

: : : How many miles are on your car? Just curious. Never heard of one of these going out on an 850.

: : 105k

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