Both front and rear differentials work in a exactly same way.The reason why your rear wheels are turning in a opposite direction because your rear drive shaft is locked while the transmission is in park position and it cannot turn.
Your fronts are not behaving like rears because in a park position,transfer case clutch is open and front drive shaft can rotate freely even your transmission is locked.So when you try to rotate one of your front wheel,your front drive shaft starts turning before turning your other front wheel.If you hold your front drive shaft,i bet your counter wheel would spin in opposite direction.

Main difference between ISTA and snap on or similar tools besides the accuracy of reading codes is that ISTA guides you through test plans according your fault code.

Thanks for clearing that up Ninja. Makes sense. I saw a few ista setups for sale on ebay; they are fairly cheap so i'll give that a go.

Also look for any signs of water intrusion in the trunk area where modules are and around front passenger side fuses panel area.

Happy Thanksgiving everyone too!
As ninja_zx11 said there is a big difference between ISTA and any other tool(for BMW). The way the codes are described in detail(well, most of them) and test schedules it performs will give show you the real picture and are not available with any other tool. And just a piece of advice: look at the modern car as a sytem. Engine not cranking doesnt mean a starter problem and code for the TC doesnt mean it is the TC it self.
When you turn a front wheel he torque you applied will look for the path of the lowest resistance. Because the transfer case has the front axle un-coupled normally, it will be easier for the front driveshaft to spin than to turn the other side axle with the hub, brake rotor, wheel and some brake resistance. So I would say it is a normal behavior.
You dont have to buy ISTA from ebay. I can help you t install ISTA/D (diagnostic only) on any Win7/8 laptop and then you can decide to buy ICOM or K+Dcan cable for vehicle interface.

Hi Bawareca,

I have a friend who has a bmw diagnostic setup but does not support my model (he was the first person I called). His model i believe is called DIS installed on an old thinkpad. Would his cable suffice for my model (it was able to read my old 08 750). I have a laptop with windows 8. Maybe i can get to work faster than i thought!

Also, is this link floating around the web,

Cheers.

DIS will not diagnose E70 and DIS testing schedules are not very good.
I will PM you with the link for the ISTA standalone. If you have troubles with the installation you can contact me. I believe with the Ediabas you should be able to run it with K+Dcan. Others have more experience with K+Dcan cable, I always use ICOM.
If someone else needs the download links i will PM, just not going to post them here.

Happy thanksgiving to all of you too!!
I was using Amazon $20 K+Dcan cable with rheingold and it worked fine except i wasn't able to reset fuel quantity adaptation on my X5 35D.But we seldom use these kind of expert functions.
Just ordered ICOM A2 as prices have came down a lot.So i think for you K+Dcan cable should be good enough and you can use it with patched edibias 7.3.0.You just need to select "Ediabas default settings" from the VCi config settings on rheingold.Also make your cable comport to com 9 as mostly ediabas is set to run on com9 and then change the latency to 1 in com port settings.

DSC and 4X4 error often point to a low voltage condition. What's the battery voltage before starting after sitting overnight?

If ABS/DSC module can't get speed signals from all 4 wheels I suspect it can't figure out how to control the front/rear power split in the transfer case, hence the error. It sounds like it is treating the wheel speed difference as tire slip and reducing power aggressively. I would focus on fixing the lack of front wheel speed signals. The other problems may correct themselves.

Awesome guys,

thanks a lot. I whipped out my old toshiba and started downloading (this will be my dedicated diagnostic computer).

Hey Pshovest,

I agree with your input on the front wheel speed sensors. them reading 0mph while the rears are reading properly is definitely of concern. All fingers were pointed at the abs module for that reason. Hopefully when i get the cables and this thing working, i'll be able to figure it out.

thanks again everyone

In the meantime, did you try battery reset?