Reposting from another thread.... New to the forum here! Been obsessed with DIY maintenance and upgrades on my 08 335xi e90 since I got it a couple years ago. I've been hunting down what is either my front diff going out, a bad wheel bearing or...??? Today I put her up on jacks and pulled the entire front underbody off along with the metal brace/tray. Cleaned everything, inspected for leaks, and anything blatantly wrong. I've got an oil leak coming from somewhere. I recently did my oil filter housing gasket, new valve cover & gasket, had new turbos out in about 5k ago and have been totally anal about fluid changes. Tcase, both diffs, AT fluid/sleeve/filter all in last 4k miles. I was told I had a small leak in my 'bed plate' when my turbos were replaced under the extended warranty. They offered to fix for $6k and I declined as it was way too much and nobody I found online had ever heard of it...no documented bed plate leaks anywhere online for the N54. Now I'm a little panicky as I'm starting to think it may indeed be a bad seal/gasket on the bed plate. Ugh!!! Found a little play in & out in both half shafts but no leaks....CV boots are nice and rubbery/new looking. I pulled the fill plug and decided to drain the oil.... got a little more than a half a quart out....not good. Filled back full. Noise still there. Pronounced when get up to 40+ mph....let off gas and it gets loudest....throttle and it gets quiet....gas again and it quiets down. Either bearing or worst case my front differential gear is worn?? Oh joy!!!
sounds like your having fun. I have yet to see a bed plate leak on a N54 motor most the time it is the oil pan gaskets that leak. Does your bearing noise change when drifting the car left or right. If it changes then you can say it is a wheel bearing and tell which side. But from what you described looks like you might have diff issue. If you can put it on a hoist and see if it makes the same bearing noise that would help to locate it.
Wheel bearings tend to get louder and more noticeable when turning, such as when changing lanes while cruising at some speed, say 35 mph up to highway speeds. A super-fast lane change isn't needed, just quick enough to put some load on one side or the other.
Thanks, guys. Sorry for disappearing. Crazy busy the last couple of weeks. Yes...I sure am having a good time! I haven't been able to notice any big change in the noise when cornering and especially not lane changes. The of thing is the car runs great. No drive train vibrations or lights etc. Inspected all drive line joints, CV axles, boots etc all loom brand new. One thing that is of concern is the play in/out with each axle shaft. I have read that is normal, however so curious on concensus of acceptable amount of play. The really odd thing is this literally walk started within hours of installing my KW V3's and Vorshlag plates. Coincedence? Or did I do something during tear down and install? I made sure to be careful when pulling each wheel hub/strut knuckle down for removal of the strut. I've read of people pulling the half shaft doing that. Mine seem well secure. Ugh. I don't know. I'm going to pull apart the passenger front hub and replace the bearing tonight. Thanks again for the feedback. I will keep this updated. At the very least....I'm getting a great lesson in diagnosing and learning all aspects of the xi front end. Also just took delivery of some brand new Avant Garde M359 hyper silver wheels. Gonna go mount them and enjoy a little eye candy before likely spending a couple days in misery doing the bearing swap. Cheers, fellas!
