Gearbox oil change

[drummerboyXJR]

My XJR x308 has recently needed a lot of revs to make it move on these cold mornings, almost like clutch slip on a manual?
Is this a common feature of auto fluids, seems fine once its warmed up. Am thinking maybe the fluid is too viscous when cold to do its thing in the torque convertor? Am a bit vague on the workings of auto boxes.
Have read a lot of info about recommended fluids, is the changing process a bit easier on the Merc box?
Any tips would be appreciated, thanks.

[Cecil]

The JEC did a feature on changing the fluid on both the Merc and the ZF box, a few months back, good article.