Are you sure it's a "clunk" and not a metal screech or pop?
Assuming it's not something as dumb as nuts and bolts not being torqued down properly, the most common cause of coilover noise is the springs rotating under compression and grinding against the perch/mounts. This is not a Z problem, it' s a universal coilover problem for any units without thrust washers or bearings.
also, the "Nismo" coilovers you got from the factory aren't Nismos.
They're rebranded KW's, the last we looked at it.
They should be using rubber mounts everywhere as they're comfort oriented for soft drivers.
As a, minor, update - I had my local mechanic look it over and there was nothing 'obvious' found. I'm taking it to Nissan on Saturday.
I still don't know which direction to go if they tell me the sound is 'normal.' I honestly can't believe that will happen as the noise is very noticeable and loud. But, trying to be prepared for that so I know which direction to go - springs, or different coilovers.
As a, minor, update - I had my local mechanic look it over and there was nothing 'obvious' found. I'm taking it to Nissan on Saturday.
I still don't know which direction to go if they tell me the sound is 'normal.' I honestly can't believe that will happen as the noise is very noticeable and loud. But, trying to be prepared for that so I know which direction to go - springs, or different coilovers.
