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Transfer Case Actuator potential free fix!

790K views 1K replies 251 participants last post by  jayram1408 
#1 ·
A couple weeks ago, I got the "terrible triad" of lights (ABS, 4x4, and Brake). Recently, I got the clicking noise after turning the car off and was able to determine that it was coming from a transfer case. Using several posts from here, especially this one:

http://www.bimmerfest.com/forums/showpost.php?p=4473836&postcount=19

I bought a new transfer case actuator and installed it. Problem solved, no lights, no clicking, all better. It is not a cheap part at 720 bucks from getbmwparts.com, and 900 bucks elsewhere, so the engineer in me wanted to figure out why they were failing.

Which brings me to the purpose of this post. I disected the old actuator to find out what the heck is going on inside it. I appologize for the huge pictures, but some sort of resolution was needed to describe what I was trying to say.

What the actuator looks like when off the car:


And broken down into the pieces: Bottom right is the motor, top right is the brush assembly, top left is a guard of some sort that pops off (albeit bent and unusable once you have it off) and the bottom left is the gear assembly (we'll focus on this one)


After I popped off the oil guard piece, here is what the inside looked like, a ton of shavings and grease.


and closer:


So you can see the motor turns a worm gear which is mated to a black gear (which is made of plastic :thumbdwn:!!!) Eventually, this gear wears down like crazy and doesnt have any teeth left to grip the worm gear. This is what causes the slipping, and the error lights, and especially the clicking sound.

In this photo, you can see the change from good gear area to the bad area. The good area is on the left, and as you follow the black gear around to the right, you can see where it has been worn down from sitting all the time.




So, I went farther. I took off the black gear to see what it looked like:
Good side (what it should look like everywhere):


Bad side (Cause of the problem)


POTENTIAL SOLUTION:

So now we know what the cause is, how can we fix it? It has been (from my research) that everyone just buys a new actuator. Yes, it fixes the problem, I can vouch for that, but I don't know how many other people looked into what CAUSED the problem.

I bet you could unbolt the motor from the gear housing assembly (it is held on by 4 torx bolts that come off quite easily compared to trying to remove the actuator from the car).
Mark a location of the current position on the white plastic gear you can see in the first photo. After the motor is unbolted and removed (ONLY THE MOTOR, DONT DESTROY YOUR ACTUATOR AND TAKE THE WHOLE THING APART!!!!), turn the white plastic gear 180 degrees from its current location. This takes the bad part of the gear and puts it where it will not get used, which means that a good part is now in contact with the worm gear.

Re-insert the motor and bolt back together. This should give you, say another 65k miles (when mine failed) or so before you likely have to replace the actuator. Re-install on your transfer case, and voila! you should be good to go with only an hour or so of your time wasted instead of time and 900 bucks.

I haven't tried this, so try it at your own risk, but with pulling everything apart, it seems like a pretty safe bet, but obviously I can't be held responsible if something does go wrong.

Hope perhaps it can save someone almost a thousand dollars. I believe my logic is sound, but I look forward to your comments!
 
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#4 ·
OK. Engineer here. Not quite following your description of the gear reversal and how that 'fixes' the problem, so maybe I'm missing something critical, but:

I don't think reversing (or simply rotating, if that's what you're suggesting) the exposed white gear 180 degrees will correct the problem. Yes, that could re-position a 'good' portion of the black gear onto the worm gear, but regardless of how the gears are positioned, as all of them turn, the black gear will rotate until its worn portion reaches the worm gear, then it stops turning again. This will happen within one rotation of the black gear.

Based on the wear that you highlighted on the black gear, I think it would have to be replaced -- if one can find the part...
 
#5 · (Edited)
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)

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?

Again, I guess it might not be a fix per say, but it could seriously delay the need to spend 900 bucks.

Just a thought.
 
#11 ·
What I think you are looking at in the top picture, top right hand side is a brushless DC motor, which would be controlled by output from a computer that would tell it to turn a certain number of revolutions in a specific direction. It is likely that the drive gear never does rotate 180°, so rotating the drive gear may work.

The concern would be why the gear wore out. It is obviously being overloaded, which could either be a processing problem in molding the gear or it could be that whatever the actuator is trying to turn is not turning a freely as it is supposed to.

At any rate, it would definitely be worth a try. The only downside I see is expending the time to remove the actuator.
 
#18 ·
no one has tried it, you would be thre first one!

I'm really curious as to if it would work. It might, it might not. Do you have the clicking noise when you turn off the car from underneath?

To do the "fix", all you have to do is unbolt the actuator motor (I think you said you did this already), turn the white gear 180 degrees, and put the motor back in. The worm gear will seat itself properly (I have tried this with my messed up one, so you should have nothing to worry about). Reinstall and then let us know!

If you can drive a few times and try to push the X-drive system so that it has to work, and report back many of us would be very eager to hear how it works. Good luck!
 
#23 ·
I see good logic in both of those. It will be interesting to see if more people can have success with this. Either way, I would mark the bad area somehow so you know which way you turned it. I could see 1/3 turn working, but I wouldn't go much less than that.
 
#31 ·
Hi,

Excellent post. Can I ask, is this something I need to be aware of on my 2005 330xi sedan?

Chuck
Yup...same transfer case. Or at least very similar...
 
#30 ·
well, twice now (in 2000 miles) I get a clicking sounds from under the car when I turn the engine off. Some kind of loud clicking, like a diesel truck turning off engine - kind of noise.

No lights at all. I am wondering if it's the precursor or this actuator failing? 61000 miles on the car , and looks like about 2 years in a snow region.
 
#32 ·
Crenninger
The clicking sound its the transfer case actuator in my case it started at 66000 miles with the clicking sound then one time all light came up (ABS, Brake and 4*4) turn off the engine and they where gone for a while the came back again. The actuator its around $800 but if you want you can do this fix and it works mine stillworking fine since i did it. Its only been three days but i will keep posting if anything happens.
 
#37 ·
Not sure why, but according to this earlier thread, even an indie shop charges about $300 for R & R of the actuator (and twice that at a dealership):

http://www.bimmerfest.com/forums/showthread.php?t=515960

If there is some substance to needing to update the ABS computer when the transfer case and/or actuator is replaced,
I could see 1 hr. min. for R & R, plus 1 hr. min. to connect up to the computer plus time to refresh s/w.

Wonder if that computer update step is really needed to configure a new actuator?
And if it is needed at all with the quick fix?
 
#45 ·
Like I said in the first post of this thread, I installed a new actuator. I didn't do a configuration with a computer, it was simply plug and play for me. Its been a couple weeks since I did the replacement, and we have had some serious rain, and I have had no issues yet. It shouldn't be needed at all if you attempt the quick fix. For all the computer knows the same stuff is there, it just isnt't throwing error codes anymore.
 
#46 ·
Excellent thread pburnett :thumbup:

My '05 is only at 51K and I'll remember this little trick if I run into the problem in, oh, say 15K more miles or so. :)
 
#47 ·
Mercedes G500's have a similar problem - an expensive actuator is disabled by an inexpensive gear. On those cars, the actuator cycles thru every time you start the car, so even if you never use AWD, the part wears out eventually. On the Mercedes the ignition won't work at all if the unit does not cycle correctly, meaning sometimes you have to try starting the car a number of times before the unit orients correctly. There are a few remanufacturers that will do the units fairly cheaply, and some people have reported success in finding the $20 gear instead of the $700 unit. Might be worth looking into as far as the X3 goes.
 
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