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Short springs, upper pan, isolator, clunk!


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Rear suspension.

 

I have Tokico springs that lower the car 1". They are too short when the suspension is at full droop by about 1/2" so I zip tied the springs to the upper and lower pans to keep them from ever jumping out of the pans.

 

I used to run my rear Illuminas around #1 or #2 on the street but last Fall I switched to #4 and installed LCA camber bushings. Since then, I have noticed a metallic thump under very specific road bump conditions coming from the right rear.

 

I checked and double checked all possible pivots and mounts of the rear suspension. Tonight, I noticed that with the car jacked up, the rear spring pulls the upper spring pan down from the upper isolator about 1/4" or 1/2" at full droop. I put a jack under the rear LCA and jacked it up and down to feel the slop. The play is between the bottom of the isolator, and the top of the upper spring pan. I feel it on both sides but more on the right rear side.

 

It has been a long time since I had the rear struts apart. Is it normal for short springs to unload the upper spring pan from the isolator under droop? Also, setting the Illumina to #4 may cause the rebound to be slow enough so that when driving over an abrupt dip in the road, the upper pan gets unloaded, pulls away from the isolator, and then bangs back into it with a clunk, as the suspension reloads/rebounds?

 

Is my hunch probable? What's the fix without going through a major overhaul, unless it needs one?

 

The clunk is almost gone when I have a passenger. I suspect because the right rear suspension is more heavily loaded.

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Is it normal for short springs to unload the upper spring pan from the isolator under droop? Also, setting the Illumina to #4 may cause the rebound to be slow enough so that when driving over an abrupt dip in the road, the upper pan gets unloaded, pulls away from the isolator, and then bangs back into it with a clunk, as the suspension reloads/rebounds?

 

Your might be correct regarding rebound. If cut cut off the wire ties holding the spring to the upper and lower seats you might find the noise goes away. Also, check the gland nuts and make sure they are tight in the strut and are tight on the shock.

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