I just purchased a 2011 Infiniti FX50. While driving over rough roads I hear a

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thumping noise coming from the driver front suspension area. Infiniti service manager informed me it was shock. Prior to this I had a 2010 FX35 with the same problem. Another mechanic solve the problem on the FX35 which was the ball joint and the arm had to be replace and not the shock. How do I find a trustworthy mechanic to be honest and resolve the problem. My gut tells me not to trust the Infiniti dealership because I have caught them in several lies in the past. Any help would be appreciated. The FX50 has 54,000 miles. Thanks In Advance