Does this clunk occur only when you accelerate or brake? This has been a long discussion over on ClubGP for some time; Haven't looked in the thread in some time.
I can't really search for it right now. But IIRC the consensus was the Sub Frame Bushings. For $100 and about 30-60 minutes of your time you can have all 4 of them replaced.
Ok Check
Other thing it could be are your motor mounts, suggestion here is to go with the solid rubber motor mounts, easy enough to do. Do a half set of engine spacers from VinnieGTP if you plan on lowering.
Check, but question can I do this prior to the drop?
The one other weak spot that doesn't really come up often are the LCA's. The front mount on our LCA's are a rubber bushing and can't be replaced by itself, you would have to replace the whole LCA. I suggest the W-body store replacements, regular or performance it is up to you and your budget. This will take of your other bushing and ball joint. The only way to eliminate those front bushing is to go to a solid mount, but there are only 2 options. ZZP tubular's....that break and the 10 sets of Ron Vogels that are next to impossible to find.
So is this what you are recomending for the LCAs? And am I hearing that the ZZP upgrade option is not worth the money?
Control Arms (Pair)
You should check your Front Sway bar and make sure that the mounts are still firm and attached to the subframe and that your sway bar hasn't rotted out and broken. Dorman makes a $100 solid sway bar replacement that is perfect. Ebay.
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For the Trailing Arm, I suggest the ones off Ebay by BMR or UMI (I can't remember the names specifically) but for the cost its a better option than what ZZP has to offer.
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Strut/springs are up to you. Doing your own spring compressing and mounting is fun and probably cheaper. I HATE KYB, their customer service attitudes when I call them is just the icing on the cake. But seeing as its either OEM, Bilstein, or KYB. Its basically all we got, do look into Bilsteins with spring of your choice and if you can afford it...go for it. Bilstein is a better strut period. Remember to replace your top mounts.