mlvswoll

I own a 08 535i and have noticed a "howling" or low pitch screeching noise while steering at low speeds. It is brief and happens intermittently without cutting the wheel fully. I have found info pertaining to noise in the steering on E60's and the existing bulletin for adding Lubrizol to the power steering fluid. However my car using the Pentosin fluid for power steering and this bulletin fix does not apply to my vehicle. Just wondering if anyone with the Pentosin fluid in power steering has had this corrected. I also found a strange thread suggesting you change the rear diff fluid to eliminate noise. Not sure how that would come into play with noise in the steering rack, but I'm open to suggestions. Thanks in advance for any info you guys can contribute.