[E92_William]

Hello, ive been diagnosing this horrible noise that came to the car a few weeks ago. Its a dry roller bearing type noise that happens from a stop till you get to like 40mph then it becomes a bad bearing hum.

https://youtube.com/shorts/a-KW7tYP-p0?feature=share

I went through the absolute hell that is replacing both front wheel bearings and it stayed.

Jacked the rear of the car up and ran it on jackstands and the rattle was coming from the front output shaft.

(My car has no front driveshaft and no cv axles on since 60k miles ago so almost rwd)

Removed the output shaft and plugged it with a plastic cap and went for a drive and still does it…

Has anyone had an internal bearing or something fail in one of these atc300 cases? I dont want anything to do with the xdrive system in this car so if I could do something to get rid of the noise that’d be perfect without having to go as far as swapping the transfer case in which case I would just put a rwd transmission in, maybe flashing xdelete could get rid of this noise depending on where its coming from? Thanks.

[jadams161]

The ATC 300 does go bad...usually due to low fluid. They only have about 16 oz of fluid inside. I just replaced mine at 138k..wasn't horrible but it was run for a long time by last owner with almost no fluid inside and had some bearing noise. If you are going to replace the Xcase I would say to just buy whatever you need to go full RWD.

[E92_William]

Originally Posted by jadams161

The ATC 300 does go bad...usually due to low fluid. They only have about 16 oz of fluid inside. I just replaced mine at 138k..wasn't horrible but it was run for a long time by last owner with almost no fluid inside and had some bearing noise. If you are going to replace the Xcase I would say to just buy whatever you need to go full RWD.

That is most likely the reason why mine crapped out aswell, I think it might have been leaking out of the rear output shaft because I went down there and there was hydraulic oil on the mount brace and no oil came out when I removed the front output shaft. No oil around the actuator or front shaft so thats the only other leak prone spot.

Going to try filling it up today and see what it does but im sure the damage has been done.

I thought about manually putting it in rwd mode through the actuator but after studying the design, it already rests in full disengaged and rwd mode unless the actuator actually forces the clutches together so nothing much I can do there.

[E92_William]

Filled it up and nothing changed, the noise goes away as the car picks up speed. I have it on ramps. When the car is in D at idle it makes the noise and as you speed up theres some sort of mechanical override in the transfer case that cuts power to the front output shaft at speed and the noise stops completely. Ive been looking at internal diagrams and videos of the case and the clutch is kind of spring loaded so makes sense. However I have no way of controlling when that override happens because the transfer case actuator its like it engages no teeth in the hole for whatever reason, and I checked theres no broken ones in the case so.

Whatever only way out of this seems to be to replace the transfer case in this car and sell it and or pick up a rwd e92 and swap my nice options over and sell this one. Converting to rwd fully seems like a massive hassle but I’ll weigh my options. Thanks for help

This video of this guy that had a failed case perfectly shows what actually went down and why the actuator cant touch any of the teeth, very difficult to try and pull it back around as you only have access to one of the arms of the clutch pack through the servomotor hole.

[Brian86]

Yikes. That's unfortunate. It doesn't help that the BMW fluid doesn't lubricate very well. It feels vastly inferior to a gear oil, in favor of having the right wet clutch friction characteristics. (at least that's my bumpkin 'squeezed the oil between my fingers' impression)

I've gone against the common advice and switched mine over to redline about 20k miles ago. Will advise if my T-case explodes because of it, but it's working fine so far.

Should be able to get a used T-case for about $200.

www.car-part.com

Punch in your vin number. The car-part web portal is very good about X-referencing the appropriate makes and models.

My e91 is using one out of a 5 series that had ~80k when I got it.

[Saico]

Hey William,

If you were driving with driveshaft off then your TC is probably toasted. The noise you are describing may be from roller bearings inside the case. If you are a DIYer you can have a look inside yourself. You need to detach the exhaust and main prop shaft and a few screws holding the TC.

[E92_William]

Thanks for the help and advice guys, I ended up finding a unit on eBay from myautostore from a 335 they were parting out for quite cheap around $200 and it had 108k miles. First thing I did was check the fluid on it and it was very low, that’s how all these cases are failing I bet. Changed it out with some from the dealer as my fcp order is in limbo.

Replaced the transfer case yesterday and took it for a drive today and everything seems to be working great, car drives good and surprisingly my 4x4 light trifecta is gone, however I’m not holding my breath as I think they will come back since I’m suspicious about my control module.

I think the job seems a lot scarier than it is, all I had to do was remove the exhaust, unbolt the guibo and the transfer case bracket and the thing was ready to come off, 2 people helps for the job a lot.

Will be opening up my old case to see the damage in the future.