Repair manual does not call for preload, just good straight alignment. I have not been able to find anything related to skewing the carrier to achieve preload. It should be installed perpendicular to the long axis of the vehicle. I believe these are tapered race roller bearings, so if you must preload, make sure the small end of the taper is in the same direction you are loading to, otherwise, you will really help the bearing to disassemble itself further down the road. Just put it in lika da booka saysa to doa.

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Jeff L
1987 300e
1989 300e
1987 BMW 325