Stats on my car:

• WS6 88 Formula
• 150K miles
• KYB GR2's on all 4 corners, with under 5K miles on them
• all suspension components appear to be original

I decided to ugrade my car's suspension with an Eibach Pro-Kit Lowering Springs kit (p/n 3801.140).

• I took the old springs out without issue and installed the new springs without issue either.
• The rears were a piece of cake and I properly indexed the springs into their isolators. I did not remove or replace the panhard bar in the rear when I dropped the axle to remove/install the rear springs.
• I purchased new insulators for up front.
• I did not replace any bushings in either the front or rear. They looked well-worn on inspection but not like they were in dire need of replacement.

Symptoms after install:

• metallic clunking noises from front and rear after install even from hitting minor potholes and bumps
• car bottoms out going over highway bridge joints (violently) and speed bumps
• I get wheel hop if I go over several bumps in rapid succession at highway speeds

I can't figure it out - it's like the car's suspension geometry is rejecting the new springs which are supposed to lower the car 1-2". Has anyone else experienced this?

 

Sounds like the shocks are shot, 5k or not. Maybe just the rears.

 

hmm good point. are the GR2's known to have quality issues?

 

Interesting story.... I just redid my rear suspension with KYB Gas-ajust shocks and eibach pro kit springs. I also changed out the sway bar endlinks and bushings. The rear is much more solid for me than on stock. I also have the front eibach pro kit springs and KYB Excel-G (i think GR2?) for the front but i havent gotten to it yet. So far for me the back is good. Im getting 'ready' to get my front end done, but im collecting parts to rebuild it all at once.

 

It is most likely the shocks. I bought my car with Eibach Sportline springs and a Gr2's all around. It rides terrible, period. New "stock replacement" or "stock upgrade" shocks won't cut it IMO. I will be putting a set of Koni yellows in my budget plan in hopes of not having to buy shocks ever again.

 

Welp - sure enough the passenger rear shock was shot. It was a pretty catastropic failure for such a simple part, too - the lower mount on the shock was competely sheared off the shock body and the shock was totally dead.

I swapped out the Eibach Pro Kit in favor of a set of Trans Am spec springs from MOOG which I figured would have been used for a factory WS6 car with heavy duty ones in the front. I also installed isolators on the upper and lower body contact points up front and threw a set of Energy Suspension poly bushings on the rear spring perches. It rides much better now.

Should ride much better in a few days when I swap out the failed KYB Excel G's installed in the rear and replace with the dial-adjusted KYB AGX units. Pricey but well worth the investment

 

I had ride quality issues with GR2s and Moog 5662s
Bad ride quality and clunked hard when driving over bumps.(only in the front)
The issue was actually the strut mounts
after replacing them with J&M solid mounts, ride quality drastically increased
The stock mounts were close to failing all together.

GR2s aren't designed to be used with lowering springs, so that might be another issue.
​​​​​

 

The AGX I feel are the best for the buck. Not as pricey as Koni! I know the fronts are even more $ but you should install those also. Ever since I put the AGX on all corners it made the biggest single improvement in the handling dept.