Possible Transmission / Front Driveshaft Failure *edit* Rear Axle popped out

[andrewwynn]

Can't tell which joint I'm looking at. Is that the "goesin" of the back diff ?

[SRacin]

Originally Posted by andrewwynn

Can't tell which joint I'm looking at. Is that the "goesin" of the back diff ?

Yup right rear diff output shaft to CV. have just updated previous post with further info

[SlickGT1]

Congratulations. That went from a supper scary situation to a free fix.

That’s crazy that the car monitors rear. But good to know.

Yea front won’t give you any errors with no drive shaft. We had a person on here that discovered by sheer accident that the front drive shaft was completely gone when they purchased the car. I also had my front pop out due to a defective clip. Car doesn’t care at all.

And my friend at OMG removes the front driveshaft constantly when diagnosing x drive components. Car doesn’t care when front is missing. I haven’t verified a front drive shaft off situation myself, but I have verified the popped out cv and no errors at all.

[andrewwynn]

I guess the x drive just senses no resistance and shuts off the front power. I've been led to understand you needed to pull the fuse to the motor that disengages the front axle.

I remember the guy who discovered he had no front driveshaft, I figured he had the equivalent fuse missing.

Good to know that the x-drive will keep on chugging when something blows up front but it should definitely give you an error when the front is disconnected why else is there a 4x4 error light on the dash?

The car doesn't have a separate sensor for wheel speed vs CV to detect a defect like CV pops out but it knows the calcuaked car speed from the transmission output shaft I guess only the rear wheels are accounted for in that math.

(Because the error that showed up in the his case was "transmission output speed too fast compared to wheel speed". ) it's very interesting that the front output is apparently ignored

[SlickGT1]

As far as I understand. The fuse takes out power to the actuator with the plastic gear only. The car is inherently rear wheel drive without that actuator. But you will get an error in the computer when you pull the fuse. Remove front driveshaft though. And car doesn’t care one bit. And no errors. I think the idea behind it is that the xdrive can be rear only, but never front only. So computer only monitors what’s at the rear.

Anyway. Not the first person to have a rear half pop out. Happened before on here. And same story. Work was done prior.

[Astrok]

I had extract same failure and did lean a lot about BMW all wheel drive. This seams to be odd failure and not much experience on forum. I did post some learning in Bimmerfeast “ question about Transfer case” I do not know what let the axles pop out I just replaced my differential with one from junk yard. Did not want to chance it doing it again. Side note my power train is much quieter and smoother with replacement Diff. I did not realize it was getting louder!

[andrewwynn]

BMW brags that all power can go to any wheel with xdrive but probably only when the brake holds the back from turning. It's very odd that you get no error with the front drive shaft gone.