My 550 XP did that. Awful grinding noise when using ADC. Read a post somewhere to change front differential fluid. Poster recommended using new Polaris Demand Drive Plus which works for ADC and front differential. Changed differential only and noise is gone and ADC works. Poster also recommended not to use ADC unless really needed it. That will be my plan also. The diff fluid in machine was black and dirty. Poster recommended checking to see if fluid was black and changing it if it was. Only had about 700 miles on 550 at the time.
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