If it's an M54, you'd be crazy not to do the oil pan gasket while you have the diff out as well.

"If" this is front diff, 50sKid posted a nice youtube video for E83 (2004 X3) oil pan gasket.

You can see that between 23:30 and 26:45, the front diff came out.
No need to drop subframe. I understand this is E83 X3 but E53 X5 should be similar...

https://www.youtube.com/watch?v=wMIr8hDmB1Y

O.P.,

How many miles on your X5?

2005 X% Won't move on Hard Turn
 

Alright,I got the front differential out and opened the differential case and didn't find anything broken or out of place. I tell you it was a bitch to get out. The Bentley manual makes you think it will come out just pulling the driver's side3 shaft which is not so. Anyway,no broken parts, no metal shaving, any ideas?

I also checked the plastic gears in the transfer case actuator and that's fine. I'm at a loss at what next to look at.

Another potential bind spot would be the CV joints of the front axle, especially if this "lock up" is only occurring on sharp turns. There are spider gears in the transfer case as well, but I would expect you to be hearing a lot of noises from that on any kind of a turn when the two axle shafts have to spin at different speeds.

2005 X5 Won’t Move on Hard Turn
 

In case anyone is interested in the outcome of my problem. I removed the front differential, which was a total bitch, and found nothing wrong with the internals of the differential. I did however find a trashed driver side motor mount and a bad flex disc where the front differential connects to the drive shaft. Replaced those, put everything back together and it's working just fine. I don't know if maybe the combination of the bad motor mount and flex disc caused some weird geometry at full steering lock but the problem is fixed. While it was a major PITA, I did have the opportunity to replace the bad parts (of course) but also allowed me to do a complete fluid change, find a bad passenger side ball joint and replace the front pads which were pretty thin. Thanks for helping me try to figure it out.

Wow, what a weird problem. Good job for figuring it out! And thanks for posting the resolution!


Since the front axle goes through the oil pan, a bad motor mount may have cause some kind of binding of the axle itself, which might have caused that problem. Anyways, good work for diving in and figuring it out.

Thanks for following up...

I had a similar situation caused by a bad wheel speed sensor that caused the ABS to lock up. I had to rock the vehicle forward and back to make it go away and it would be OK for a while. I chased all kinds of things related to the transfer case, flex disk, front axle shafts as well as the front differential. I didn't just throw parts at it but it frustrated my wife to no end taking a while to diagnose. Plus it was lousy weather at the time so I wasn't too excited to crawl around under a wet freezing vehicle.

and engaged transfer case will cause this concern. next time remove the actuator and check if the motor is binding. This usually happens after the gear has been replaced, but can sometimes happen on its own.