[frisbeeguy]

Hello,

I have a 2007 BMW X3 with 102K miles on it (primarily highway driven), and a mechanic diagnosed the transfer case as bad. Basically, when the car goes over a speed bump and a hard right turn is taken, a "bump" is felt for the passenger. The mechanic showed me this issue since I wasn't aware of it. However I find it hard to replicate this scenario, and the car feels normal both on highway and city, and there are no fault codes in INPA (the mechanic also said there are no fault codes, but it's a mechanical issue.) At first the mechanic suspected the rear differential, but after changing the fluid, checking it, and test driving, he says its fine and in good condition. He also said the front differential is in good condition. When the transfer case fluid was drained, it came out as silver . However, there were no metallic particles in it (mechanic allowed me to feel it and he also felt it), so I'm assuming water contamination? I did the tranny fluid myself, and that looked fine (although dark no burnt smell and pretty much typical drop the pan, change the filter etc.)
Also, whenever I hard corner (like autocrossing...really hard), it makes a metal on metal shriek sound and the mechanic said it could be the transfer case, or brake rotors rubbing on the backplate,etc. However upon reading: http://www.bimmerfest.com/forums/sho...=463848&page=3
it seems the transfer case may not be the issue? The brake pad warning light is on (came on recently), so that may be the issue for the shriek noise? (I plan to change rear pads+rotors since the car is used and I can't find previous records for the rear ever being changed for rotors, only for front pads and rotors and rear just pads were done). I'm pretty sure the rear springs are in good condition (based on visual inspection)?
Basically, could the transfer case be the issue, or is it most likely just nothing and I should just drive the car like normal and just do the brake job? Any way to really test the transfer case? Should I get a second mechanic's opinion? Any other thoughts?
Thanks

[rothwem]

The X3 uses a different transfer case than the E9x cars do, you might have more luck on xoutpost or another X3 site. The transfer case used on the X3 is the same as the one on the X5 btw.

The main difference is that the X3 transfer case uses a chain to drive the PTO, the ATC300 in the E9x cars is gear driven.

[Patsphan14]

Originally Posted by rothwem

The X3 uses a different transfer case than the E9x cars do, you might have more luck on xoutpost or another X3 site. The transfer case used on the X3 is the same as the one on the X5 btw.

The main difference is that the X3 transfer case uses a chain to drive the PTO, the ATC300 in the E9x cars is gear driven.

Rothwem - Good timing! Newbie here. I have an '09 328i xDrive manual shift sedan. 90k miles. I have had three mechanics tell me the constant "whine" coming from the underside of the vehicle is the transfer case, although every mechanic (two of whom are specialists) said they "aren't 100 percent sure." Each is quoting a $3k-$4k repair (ouch!). None have said it can be rebuilt. Any advice? It's definitely independent of the engine. I'd prefer to get it rebuilt, and have research refurb parts on line. Unsurprisingly, specialists recommend OEM. Thoughts?

Thank you!

[rothwem]

Originally Posted by Patsphan14

Rothwem - Good timing! Newbie here. I have an '09 328i xDrive manual shift sedan. 90k miles. I have had three mechanics tell me the constant "whine" coming from the underside of the vehicle is the transfer case, although every mechanic (two of whom are specialists) said they "aren't 100 percent sure." Each is quoting a $3k-$4k repair (ouch!). None have said it can be rebuilt. Any advice? It's definitely independent of the engine. I'd prefer to get it rebuilt, and have research refurb parts on line. Unsurprisingly, specialists recommend OEM. Thoughts?

Thank you!

I've not heard of the transfer case whining before, that sounds more like a differential. I wonder how they diagnosed, they probably unplugged the actuator and the noise went away, which would also be the case for the front diff I think.

Unfortunately, I'm not expert when it comes to the inner workings of the AWD system and I don't really have a good suggestion on how to figure out if it's one or the other.

As for rebuilding the transfer case, I think you usually buy a rebuilt unit to swap in rather that rebuilding the one you have. I found a rebuilt tcase for $1800, which seems like a good deal. You would have to remove and replace though, or pay someone to do it, which could get pricey.

[Patsphan14]

Originally Posted by rothwem

I've not heard of the transfer case whining before, that sounds more like a differential. I wonder how they diagnosed, they probably unplugged the actuator and the noise went away, which would also be the case for the front diff I think.

Unfortunately, I'm not expert when it comes to the inner workings of the AWD system and I don't really have a good suggestion on how to figure out if it's one or the other.

As for rebuilding the transfer case, I think you usually buy a rebuilt unit to swap in rather that rebuilding the one you have. I found a rebuilt tcase for $1800, which seems like a good deal. You would have to remove and replace though, or pay someone to do it, which could get pricey.

Thanks for the reply. Two specialists and a trans shop said transfer case, but nobody really explained the diagnosis all that well. All said they could "hear the noise coming from the transfer case." I know approximately 99% less than you do, but I will keep trying. Thanks so much for the help! Great community here.