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Old 09-07-2011, 02:45 PM
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timfitz63 timfitz63 is offline
MT = Doppler Shifting
Location: Lorena & San Antonio, TX
Join Date: Aug 2010
Posts: 929
Mein Auto: 2007 X3 (MT)
Originally Posted by pburnett View Post
It looked to me that the black gear doesn't turn the whole way around, only really over that worn area. I believe BMW used a full gear as to ease the installation (not having to worry about the position you put it in)...
Maybe I need to fiddle with it myself, like you have, to really see what's going on there. But what you're describing wouldn't be consistent with how a worm gear and a cog gear typically interact.

Originally Posted by pburnett View Post
... If it continuously rotated around, woundn't the gear wear more evenly and not in a single spot about the length of the worm gear...?
It may have worn evenly until it failed; you'd have to compare the teeth on the gear you extracted from your actuator to a brand new gear.

But I think what's happening is that these plastic gears are not durable enough; they either have a weak spot or just get 'chewed up' by the metal worm gear over time. I'm actually rather shocked that BMW even used plastic cogs inside a transfer case, but...

All is not lost, though; you did a good job in isolating the weak component in the actuator! Hopefully someone can zero in on a supplier for those black gears (they've gotta come from somewhere...), and we can all re-build our failed xDrive actuators!

X3 w/6-speed & Sport Package:
A sports sedan disguised as an SUV...
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