Everything I have read recently says to NOT use ATF in the power steering system. It will work but additives in the ATF will cause premature wear to the steering box. This is why W123 and earlier steering gears wear out so quickly. I have a 190D with 320k miles with much less steering play than a 240D with 140K miles. Use Mercedes spec power steering fluid.

Using ATF short term is fine, just don't use it long term.

__________________
Current: 1975 450SEL, 83 300D, 88 Yugo GVX, 90 300D OM603 swap, 91 F150 4.6 4v swap, 93 190E Sportline LE 3.0L M104 swap, 93 190E Sportline LE Megasquirt, 03 Sprinter, 06 E500 4Matic wagon.