Note:  the old fluid is Pentosin, at $20+ a litre and you need about 1.25l
to do the job.  It is lower viscosity than ATF/Dexron-III.  I use Castrols
GT power steering fluid.  Has a VW part# on back and is way closer to
factory fill than any ATF.  Both BEntley and owners manual say ATF, I know,
but all the seals in my rack failed simultaneously about 3 months after
flushing and filling with STPs Dexron-III ATF.  My gut feeling, after $400
for getting my rack rebuilt, is that ATF will never get in there again.
YMMV.  Tim SMith

My camper has almost 143K on the original rack using Mobil 1 synthetic ATF.  I 
think the trick is to change the fluid regularly and never turn the steering 
wheel with out the van rolling.  Highway mile are good.  My other 87 needed a 
rack at 93K but I never changed the fluid.  It is also used for local driving.

Dennis H.