It happens when I turn on the a/c . I've replaced the serpentine belt tensioner , I thought it was going bad . Still doing it . And it only happens above 25 mph. I can't find any answers anywhere else ! I've also replaced the a/c compressor - cheapest eBay one I could find . COLD a/c ! Just the chatter is bugging me . It just topped 300,000 mi. I had replaced the timing chain assembly - a year ago ? About that .

 

Did you replace the serpentine belt? When you replaced the compressor, did you also replace the clutch assembly?

 

You say it happens over 25mph. Can you reproduce iti n the driveway revving motor at different rpms?

 

did the last a/c compressor seize or replaced bc the noise? change the receiver drier/accumulator? did you perform proper oil balancing, refrigerant charging by weight?