Yes, ATF is correct, have you checked the level yet? There might have been an airbubble that freed up and now you are low on fluid.
FYI, there is generally noise in any vehicle when you turn the steering all the way to full lock and hold it there. Is it that same sound, but just louder than normal?

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Olympic Peninsula, WA, USA
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2005 Mini Cooper 100k, British Racing Green/Silver-Black
04/2002 4.6is 140k, Silver/Black-Alcantara *FOR SALE*
1989 325iX 270k, Diamond Black/Black
1984 318i 370k *SOLD* (First Bimmer)
Honorable Mentions: '71 2002, '87 325, '90 325ic, '92 525it, '93 325i, '94 530i