Cadillac: 1985 Fleetwood Brougham Rear Strut Replacement, fleetwood brougham, rear struts

Question
I just had new Gabriel G56701 front struts and Gabriel G56703 rear air assist struts installed on my 1985 Fleetwood Brougham (front wheel drive). Only when I hit hard bumps both rear struts (sometimes individually) make a clunking sound that seems to be coming from near the top of the strut well. When the care is traveling on a smooth surface I hear no noise problems. When parked and I push down on each side of the rear of the car I hear no clunking sound. The air assist system appears to be working properly. My mechanic says the struts are installed properly and that they are possibly defective and not compressing properly.

Could the upper mounting nut not be fully tightened causing this clunking sound? Could the rear struts be too strong/stiff for this car and not compressing properly?  

I noticed on the installation instructions that the upper support housing mounting hole requires redressing from 8mm to 12mm. If the mechanic didn't do that, could this be the source of the clunking sound?

Any other ideas on the source of the clunking sounds?

Answer
If the noise was NOT there until AFTER these new struts were installed common sense says the struts are either defective or installed improperly.

Since your mechanic is POSITIVE that they are installed correctly, I would have another faciltity inspect the work and document the inspectiona nd take photographs of the problem to show YOUR mechanic what was wrong.

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