http://www.americanmuscle.com/pmc-to...-kit-0509.html

So my '07 GT CS has 66k and there is a knock in the rear suspension so I figure bad bushings any thoughts on this kit good or bad

 

Great question!

Prothane kicks-*** and makes some awesome bushings, you will NOT be disappointed with that kit in any way.

That kit comes with:
* 34mm Front Anti-Sway Bar Bushings
* 20mm Rear Anti-Sway Bar Bushings
* Panhard Bar Bushings
* Manual Transmission Shifter Bushings
* Forward Front Control Arm Bushings
* Rear Upper & Lower Control Arm Bushings
* Rear Upper Axle Bushing

...and will make your car feel better than brand-new.

I just replaced all the bushings on my '01 with 40K miles and WOW it feels infinitely better! Turn-in is very precise and predictable. Highway stability is greatly increased as there is less "slop" in the polyurethane versus stock bushings.

I hope this helps!

Have a good night!

 

Prothane are supposed to be very good. Doing this to a new car would probably make a big difference as most of the aftermarket parts use poly bushings and that is partly why they perform better. Keep in mind though that poly is known to squeak and create more vibration. (NVH) Often this squeeking can be alleviated with a good synth suspension grease.

However with just 60K on a 4-5 year old car your shouldn't really have too many worn parts besides maybe struts/shocks. You may just need to adjust something or possibly it could be the shocks. How is the knock occurring?

 

It is a mild knock when I hit small bumps in the road. Haven't really noticed any ride or performance changes just that annoying knock. So I figured it may be control arm bushings

 

I'd get under there (If you are comfortable.) and check around for loose parts. Springs, panhard bar, over axle pipes, sway bar and end links. You can get torque specs from an online service manual.

Also you can probably check for play in the control arms by lifting the rear.