The solution seems to be working as an italian company is producing a bronze gear. But the aspect we are trying to investigate is why this happens? Is this a problem coming from the electronic or is it a problem coming from the plastic gear that is not strong enough? definitely the BMW solves the problem in the easy way...change the TC for about 2000 €!!! and no way to have a replacement gear. Is anyone so kind to post a pic from a stripped gear?
PS: are youtalking about ATC400 or ATC500 TC?

ATC 500 in the X5 E53

ATC 400 in the X3 E83.

Ray has an X5.

oK GOT IT! :iagree:
What is your opinion about replacing the stripped gear with another one made of bronze. Here in Italy we have a company that is doing that.

Hmmm.

I suppose it makes some sense, but I would go back to why it is failing. It feels like it is addressing a symptom, instead of the root problem.

If in fact the gear is inherently weak, then I think we would see a lot more failures of these actuators. If the gear strips, it can function like a type of fusible link. Making it stronger may just move the failure point along to the electric motor.

What the actuator is doing is applying pressure to the clutch packs to vary torque output. If it strips, either it is too weak, or the torque is too strong. My gut reaction is that perhaps it is trying too hard to apply pressure, ie the normal pressure isn't sufficient and so it pushes harder, and strips the gear. If that is true, I would be more concerned about why the pressure is not sufficient. Additional pressure would be required if the clutch packs weren't initialized to the controller (which is part of the servicing procedure) or if the clutch plate friction was out of spec (which could be caused by fluid being out of spec, or the adaptations not set correctly). All of those very possible mechanical problems could cause a stripped gear. So when I hear about a stripped gear, I think more about those likely causes, than whether or not a stronger gear is the solution.

That doesn't tell you what to do about a stripped gear, I just don't know. But it does give some background to potential causes for it being stripped, none of which would be solved by replacing it with a bronze gear.

Basically we have the same approach as I would primarily investigate for the reason of the damage, but so far it seems someone had the bronze gear installed but no feedback.
I have been told that the problem is probably due to the fac that during the "set" cycle (when the engine is switched off,the actuator makes one full run open/close with the clutch in order to reset its values) it is required 1/4 of the full power thus forcing the gear.
I do also agree with the idea of the plastic gear being a kind of "fuse" (the idea is already in my marine outboard engine propeller) but it does not make any sense when BMW asks to pay the full transfer case when the fuse blows (crazy way, isn't it? with a very very high cost.
Do you know anything bout the major fault of TC. I mean, is there any evidence that the stripped gear is the main problem?
Regards from Italy :rofl:

The problem is the gear, it's made from an inferior plastic, once the motor is replaced the problem is solved, I would imagine if there was another issue with the transfer case the computer in the car would disable the DSC, ABS and 4x4 to protect the actuator from getting damage.. IMO

You also have to consider how many X5's actually need to activate AWD with significant load to the front wheels. Those of you in milder climates never really put much stress on it. We live in the snow belt with frequent melt/freeze cycles and my neighborhood is very hilly. There are times when the 4x4 light is on almost as often as it is off.

It may be a similar situation to the window regulators. Some have replaced 4 or more and some have never had an issue.

Perhaps I am giving the designers too much credit when I refer to it as a fuse. I could just call it the weakest link. My concern was that if it was stronger, then something else would just fail. I don't think that the case is designed to be serviced (certainly BMW never planned on that) so calling it a fuse suggests it should be a replaceable part, which it isn't by itself.

I don't know enough about the failures to say that the gear is the main problem or not. I just find it interesting that there are not a higher number of actuator failures.

Side question, don't you have an X3 with an ATC 400? Is it presumed to be the same failure mode on both the ATC 400 and ATC 500?

Fair point. But isn't the 4x4 light a function of traction, and DSC intervening, more than an indication of transfer case torque shift front/rear? I wonder how load on the actuator motor varies with torque adjustments.

As to the window regulators, I don't think they fail by use. I think they fail by closing the doors with the windows down. The windows are not well supported in that postion, and slamming the door puts stress on the clip. You wouldn't have to have them all the way up, but if they are even up 1", the window glass is supported better. Never failed a window regulator here.

Yes, there's a lot of things potentially going on when that light comes on. If it comes on at low speed on snow or ice it's most likely traction control kicking in and transferring power to the front as well as of braking to slow the spinning side. At least that's how I understand how it works.

I've replaced the window regulator twice on my E46. Both times it was the front passenger side which doesn't get much use. It's possible that the passenger side door was more prone to being closed with the window down because I'm dropping somebody off rather than locking the car if I'm getting out myself. I haven't had to replace any on the X5. My wife drives it mostly and she hates having the windows down. You may be on to something with your theory.