I still think its a bent axle/rim. I don't see how the clutch could be a problem making the car shake at a certain speed, because it would do it at that same RPM in every gear.
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2015 Ford Mustang GT Fastback - Ingot Silver - 6M - Performance Package - Gibson Catback, JLT CAI, FR 47lb injectors, BAMA E85 tune, Eibach Sportline, BMR wheel hop kit, UPR oil separator, Steeda shifter bushing/bracket
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