Hello,
I will try to help give you some possibilites.
This might not actually be the transmission.When this happens do you get any transmission warnings or any failsafe messages? Does this occur at certain speeds, while turning et? Thank you.
Thanks for the additional information.
I still think this might not be a transmission. What I have been seeing at the dealership on multiple X3's is that the problem is actaully the front differential. You vehicle is an all wheel drive and so has a transfer case and a front differential. I have chased multiple noise complaints that actaully seem to come from the transfer case and the transmission but have ended up being the front differential as the real cause.
I suspect that it is the front diff that is your main problem also. The only way to really check the health of the diff is to have it drained and the fluid inspected. I recommend the dealer do this as they will know what to look for. Most of the time the fluid has metal swirling around inside the fluid. This would be confirmation that the front diff is bad and would need to be replaced.
This is what I had originally thought was the problem. I do want to ask a few more questions though....you say that it happens at low speed and not while driving straight? Does this happen only when turning left or right? Thank you.
Thanks, that confirms it then. It is very rare for BMW's to have the manual transmissions fail. I have seen a few transfer cases go bad but most often the problem is actually the front differential. I would put a very high suspician on the front diff. The noise often telescopes down along the drivetrain and most often is heard actually in the transfer case or transmission area even thought the front diff is the main cause.
Please let me know if I can clarify anything for you or help further. Thank you.
In your experiance, can this be fixed or would it require a new diff?
I am not sure if you would be able to find anyone that would be able to rebuild it. At the dealer we do not rebuild the diff but only have the option to replace it. I would suggest having the vehicle checked for any leaks from the diff, transmission, and transfer case. You could start with a check of the diff fluid to see if it is contaminated with metal filings. The fluid usually looks swirly. In my experience, most often this is a front diff problem but I have seen some transfer case failures but it is not as common. The fluid check will be the best diagnostic step to determine if the higher probability is the front diff.
I have seen the front diff be the more difficult item to diangnose as it can seem like the noise is definately the tranfer case as can be heard under the vehicle and with a stethescope. I have had a few of my techs get this wrong because they did not check the diff fluid and ultimately made an incorrect diagnosis. Now they all know to check this first and most often the diff is the culprit.
I certainly hope this will be helpful to you. Thank you and let me know if I can try to help you further or clarify anything.
BMW Mechanic
Level 1 BMW Master Certification, 9 Years Dealer experience, Team Leader, Shop Foreman