@Atif - this might have been me.
I did it as a trial as:
- half way up the hill, although traction control was off (4H, Sand) - kept losing power on my first 2 runs.
- on my last try - I recalled seeing the below charts somewhere, where it mentioned that VDC/TCS is off when rear diff is engaged. It worked, engine kept up the revs.
Not sure if it's only my y62 struggling to switch off the TCS completely....