Front Driveshaft Pics
 

What do you guys think about my splines? I don't know if the splines in the t-case wear down as well, so if this looks bad I would like to avoid stripping the splines in the t-case and get a new driveshaft so I get a better bite. Thoughts?

After reading about all the driveshaft failures from worn splines, I thought I would be proactive and check things out underneath. I was having some vibration issues while accelerating so I thought what a better time to do this than while replacing my front flex disc.
When I pulled the shaft out of the t-case a big cloud of rust poofed out with it. Bone Dry! I cleaned the splines and slapped some grease on them and reinstalled with a new flex disc.

come on really?? no one at all

looks good to me . possibly wearing but looks like it was machined that way .
here is a pic of worn splines beside a custom made replacement section .
a link to the thread where you will find the man to make a replacement part when it is required .
http://www.xoutpost.com/bmw-sav-foru...problem-3.html

Wow, that is shocking, looks like it only engages about 12mm or so? BMW expects that to hold? Amazing and quite ridiculous when compared to the grizzly format engineering on the font hubs.

Shooter, doesn't look bad but unless it is prohibitively expensive I would change for a new one presuming you have it out.

As far as I looked at my transfer case with the front shaft removed, the female output of the transfer case is only that long, as the splines on the shaft are. How does a longer spline help, since half of it won't have matching splines on the transfer case female output?

You are on borrowed time with that shaft. All that orange dust is your spline teeth ground up and rusting. Look close in your first picture, 1/2 of the tooth is already ground away on the drive side. Look at the damaged one in my photo someone posted, the spline fails in the middle of the tooth, it's only a matter of time. Once it let's go, it's instant with no warning and you will be stranded. I highly suggest you have me repair that shaft. You can email me at [email protected].

Chas3, the depth of the front output coupler splines depends on the year of your x. I found out through making these repairs that somewhere around mid 03 they switched to a shallower coupler. There is still a good inch of clean spline past the damaged ones. I now make those about 3/16" shorter to be safe they won't bottom out. The new splines are a harder alloy than original and still grip the damaged spline as well. Hope this helps

I have a 07/2004 3.0d and I recently had a failed front dif. Therefore, I had to take the front shaft down, among the other cute things you have to do when replacing the front dif. Since I was worried about the splines too (around 70k miles on the X by now), I took a look at them. I admit I haven't actually measured the length of the shaft splines vs. the length of the TC output splines, but judging by the eye, they were pretty much the same length. I expected the coupler to be like double the length, or something, like the picture amacman posted in post #3, so that it made sense to have a longer shaft spline.
On the other hand, making the shaft out of a better metal compound, like you said, should help.

Overall, after getting around the whole transmission system of the X and looking at its so many weak points (TC chain stretching, TC actuator failures, splines corrosion, dif. failure, CV failures) and weird designs (front dif. passenger side going through the oil pan), I am kinda disappointed and I can't even imagine going soft off-road with the X, since it easily breaks down on the street already :)

@ racemalibu.
I had a very close look at the profile of the splines in shooters first pics and I think they have been machined like that on both sides although they do seem to have very slight wear on the drive side as you say . the original design does seem to be feeble .

The splines from the factory are done by a rolling process not a machining or cutting process. They should be straight from front to back. What you see is the contact pattern of the coupler wearing into the splines. It really shows how little the contact is in there. I have a pile of failed ends here that were only slightly more worn before they failed. I'll post some pics after lunch.