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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > All-Wheel-Drive (Xi / xDrive) Talk > Front diff and transfer case weakest link?



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      06-21-2016, 08:37 AM   #1
reaper0995
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Front diff and transfer case weakest link?

I keep seeing that the front diff is supposively the weak link in the xdrive, but I can't find any photos of the diff internals, a damaged unit internals, and I'm having a hard time finding any first hand info from someone who actually broke theirs.

It sounds like the transfer case is probably pretty good overall, but the actuator wants to change faster than the gears can handle... And still no way to control it. Does this sound correct? It would seem that IF there was a way to control it, or at least slow down its movement, then all would be fine..?

Does anyone have a broken actuator or front diff? I want to start taking these apart and trying to figure out some solutions before I go further in my setup (still a year or two away, but that's not a long time to try and solve these problems)!
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      06-21-2016, 12:07 PM   #2
floydarogers
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Quote:
Originally Posted by reaper0995 View Post
I keep seeing that the front diff is supposively the weak link in the xdrive, but I can't find any photos of the diff internals, a damaged unit internals, and I'm having a hard time finding any first hand info from someone who actually broke theirs.

It sounds like the transfer case is probably pretty good overall, but the actuator wants to change faster than the gears can handle... And still no way to control it. Does this sound correct? It would seem that IF there was a way to control it, or at least slow down its movement, then all would be fine..?

Does anyone have a broken actuator or front diff? I want to start taking these apart and trying to figure out some solutions before I go further in my setup (still a year or two away, but that's not a long time to try and solve these problems)!
I can testify that the front diff is not great. I was coming down from Timberline lodge - only 2-3 miles of the 8-mile descent - in my '01 330xi and the front diff threw a tooth or two and completely froze the driveline. Impressive 90-foot 4 wheel skid to a stop in the middle of the road. Such failures are not common, but have been reported. Note that I changed the diff fluid with Redline every 30K miles or so. Unfortunately, the front diffs (of all 3-series) take less than a pint of lube, which is dead stupid.

As for the center diff (it's actually not a diff, it's a transfer case) the weak spot is the gears. The X3 forums are the best place to look for explanations. (note that my '01 330xi had a different xfer case, so I'm not speaking from experience here). Both the drive and driven gears are plastic. The center portion of the gears - where they spend most of the time - got/get worn and eventually they cause a fault - often the DSC light comes on, sometimes there is clattering, etc. I don't believe that the xfer case's power transfer gears are actually a problem.
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      06-21-2016, 04:06 PM   #3
reaper0995
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One of the reasons I want to see an actual failed front diff (from 335xi) is to see if it was a mechanical failure, or lubrication failure, overheating, ring and pinion gears stripped, CV splines strip, etc.

To your point on the .5 pints of fluid, if they were failing on road courses or normal driving then I would tend to agree that this is a huge failure point... But it sounds like a lot of failures happen on hard or poor launches (again hard to find first hand examples).


The plastic gears are in the actuator housing, which seams to have more failures at higher power levels (though stock is common too). It sounds like the failures are from having to switch from RWD to AWD more quickly and thus strips the gears faster. I haven't really seen/heard of transfer case failures, but lots and lots of failures in the actuator planetary and worm gears.
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      06-22-2016, 06:41 AM   #4
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There is abolutely nothing plastic in E9X actuators...that was on old X3 ones,the weak part in transfer case is the Friction Clutch Assembly and front and rear flange bearing. On front differential i saw few of them with broken or very rough front pinion bearings.
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      06-23-2016, 10:23 AM   #5
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Front diff
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      06-23-2016, 02:02 PM   #6
reaper0995
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Awesome, those are the first photos I've seen inside the front diff. Do you know what the failure was? And when did the failure happen, hard launch, normal driving, etc.?

Also sent a PM to see if you still have it and any interest in selling it.
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      06-23-2016, 03:06 PM   #7
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Quote:
Originally Posted by reaper0995
Awesome, those are the first photos I've seen inside the front diff. Do you know what the failure was? And when did the failure happen, hard launch, normal driving, etc.?

Also sent a PM to see if you still have it and any interest in selling it.
I think it was from launching
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      06-27-2016, 03:59 PM   #8
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Quote:
Originally Posted by Julian2485 View Post
I think it was from launching
What symptoms were you having that made you pull the front diff?
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      06-29-2016, 11:45 PM   #9
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Thanks Julian for checking on the diff for me. I'll keep looking around. Anyone who has one, damaged or working, please let me know! Would prefer to get a manual one that has the 3.08 gears (not sure if gears changed on later models).
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      07-08-2016, 08:30 AM   #10
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Quote:
Originally Posted by xthejuicex
Quote:
Originally Posted by Julian2485 View Post
I think it was from launching
What symptoms were you having that made you pull the front diff?
Heard loud rotating noises as you accelerate it gets louder and faster. You can even feel it while driving.
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