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Old 01-06-2011, 07:23 PM
cn90 cn90 is offline
Officially Welcomed to the 'Fest
Location: Omaha NE
Join Date: Mar 2006
Posts: 13,975
Mein Auto: 1998 528i 5-sp 140K+
According to this thread
Per Charlie....The reason for the preload is to prevent driveshaft vibration on takeoff. The preload helps to counter the engine shift during take off.
This kind of makes sense, because during acceleration, the engine rotates a bit to the R side and therefore "twists" the whole engine/trans assembly, effectively "pulling" the driveshaft forward a tiny bit. Therefore by preloading, it creates a little room for picking up this slack.

It is interesting that the E9 has a preloading of 2mm:

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