: "CLUNK" Be Gone (Ground Control)



Feffman
02-16-07, 11:26 PM
Gents:

By jove I think I've got it. After some input from WW (thanks Bill) and looking at the FAQ (Reed you are the man!) I tore back into the rear suspension this evening. Pulled the shocks, noting a bit of play in the shock that isn't there when the shock is in the stock set up. Off to Lowes to buy a couple of rubber and steel washers. The fix it appears is a 1.75" X 5/8" (1/8" inch thick) steel washer installed between the Ground Control urethane bushing and the stock pillow mount (the top of the shock made of rubber with the chassis mounting bolts built in). This took the slop out of the shocks. A short drive (it's snowing again - ARGH!) seems to confirm it worked. I'll do a nice bumpy ride tomorrow to confirm.

Here's hoping!

Feff

rand49er
02-17-07, 06:39 AM
Mark, I'm eagerly awaiting your next report. You da man, if this works. That "clunk" is very annoying, and that's my best G-rated way of saying it.

Any chance you can take a pic or at least summarize the steps involved, assuming this is our long awaited fix?

THANKS!

wildwhl
02-17-07, 12:01 PM
Feff -

Glad you were able to figure something out. I hadn't considered the possibility that the GC (or WW) spacers had not *sucked up* enough of the slack after removing the factory perch spacer. Good call.

WW

Feffman
02-17-07, 07:29 PM
Guys, unless I'm deaf, installng the 1/8" inch steel spacer(1.75" X 5/8" washer) between the Ground Control urethane bushing and the pillow mount worked. The clunk is gone.

Thinking a bit more about this, a rubber washer of the same size would probably have worked jsut as well. Hopefully the steel will bring less deflection by the bushings.

No photos as I'm too lazy to crawl under the car again, taking the wheel off to snap a photo. I'll try when I fine tune the height adjustment.

Hope this helps everyone!

Feff
www.MVPTrackTime.com

rand49er
02-18-07, 08:30 AM
Mark, my memory is real good, it's just real short. Having installed the GC last October, I'm trying to picture this in my mind. Are we talking the upper perch with the washer/spacer put between the perch and the structure of the car?

Feffman
02-18-07, 10:42 AM
Mark, my memory is real good, it's just real short. Having installed the GC last October, I'm trying to picture this in my mind. Are we talking the upper perch with the washer/spacer put between the perch and the structure of the car?

Hi Randy:

At the top of the rear shock when you re-assemble the top with the Ground Control (GC) parts. As instructed by GC, you have in order from bottom up:

1) Ground Control small rubber washer
2) GC aluminum spacer
3) Exisiting CTS-V spacer
4) Stock pillow mount(part with the two mounting studs to attach to chassis)
5) GC urethane bushing
6) Exisiting upper steel washer
7) Existing top nut

See the sixth and seventh photos down on the FAQ link below.

http://www.cadillacfaq.com/faq/answers/gcinstall/index.html


I simply added a 1/8" inch thick steel washer between steps #4 and #5. As noted earlier I think a 1/8" rubber washer would work just as well and possibly dampen shock noise better. This additional 1/8" inch spacer is, as Bill (WW) noted, to take up slop in the GC set up.

Not real scientific, but I noticed the "clunk" only presented itself when dropping down into a pot hole or similar type bump, not when it compressed running into a bump. This made me think it was the shocks NOT the springs.
When I removed the rear wheel with the rear suspension in full droop, the springs stayed in place on their perches thus eliminating my incorrect theory the springs may be banging on the upper perch.

Try it out and let me know if I'm batty. The spacers/washers (steel or rubber) are readily available at good old Lowes.

Mark "Feff" Pfeffer
www.MVPTrackTime.com

Seattle CTS-V
02-18-07, 06:03 PM
This is good stuff. Since I would probably hire this out I'll wait for one more positive fix b/f calling up my mechanic! Good work.

Feffman
03-10-07, 08:30 PM
Gents:

Just finished installing the front Ground Control suspension components. Without a doubt, this is how the car should have come from the factory (IMHO) as the roll is reduce substanially, cornering much flatter. I've still a little height adjusting to do at the rear before my first track day in two weeks at Heartland Park in Topeka Kansas.

I have the 500 pound springs in the front and the 550 pound springs in the rear, essentially the stock Ground Control setting. With my highway mileage and the roads around St. Louis, I'm not sure I'd go with stiffer springs.

For anyone wanting a little more aggressive look adn better handling, I'd highly suggest the Ground Control kit.

Happy Motoring!

Feff

PS: Still no clunk from the rear with the additional spacer install! :)

Venomous-V
03-11-07, 11:42 AM
I put the spacer in and it reduced the clunk. still not completely gone on big bumps or pot holes but defenitely helped. i used the 1/8'' steel spacer so i may try a rubber washer instead or just add a real thin one.

rand49er
03-11-07, 12:51 PM
Good to know ... thanks.

I hope to get to mine in a week or so.

wildwhl
03-11-07, 01:24 PM
A weak Sunday a.m. attempt at humor...

Ground Control to Feffman
Remove your factory springs and bolts ours on
Ground control to Feffman: commencing install game is on
Add 1/8" shims or spacers and may the diff gods be with you...

This is ground control to Feffman, you've really made the grade
and the posers want to know whose shoes you wear,
are they 18's, 19's, 20's or who cares?

This is Feffman to ground control, I'm spinning through third gear
and I'm clunking in the most peculiar way
but the wheel hop seems very different today

For here am I speeding in a tin can, sliding across the road
Lights in the mirror are blue and there's nothing I can do

Though I've passed a thousand miles, I'm feeling very ill
And my efforts at reducing the dreaded clunk show
tell my homies I'm a stud (they know!)

For here am I speeding in a tin can, sliding across the road
Lights in the mirror are blue and there's nothing I can do...

Feffman
03-11-07, 01:47 PM
A weak Sunday a.m. attempt at humor...

Ground Control to Feffman
Remove your factory springs and bolts ours on
Ground control to Feffman: commencing install game is on
Add 1/8" shims or spacers and may the diff gods be with you...

This is ground control to Feffman, you've really made the grade
and the posers want to know whose shoes you wear,
are they 18's, 19's, 20's or who cares?

This is Feffman to ground control, I'm spinning through third gear
and I'm clunking in the most peculiar way
but the wheel hop seems very different today

For here am I speeding in a tin can, sliding across the road
Lights in the mirror are blue and there's nothing I can do

Though I've passed a thousand miles, I'm feeling very ill
And my efforts at reducing the dreaded clunk show
tell my homies I'm a stud (they know!)

For here am I speeding in a tin can, sliding across the road
Lights in the mirror are blue and there's nothing I can do...


Wife, both kids and I are rolling on the floor with laughter. Nothing like a little David Bowie (circa 2007 for a V) to arise to on Sunday morning!

Feff

rand49er
05-01-07, 06:27 PM
Okay, just got done doing the fix and took a ride. WOW!!! IT'S QUIET AGAIN!!! :D

Thanks, Mark! :highfive:

(PS: I had to use 3/4" ID washers. Got some with 0.645" -- bigger than 5/8" -- and they wouldn't go on. :confused: )

SoCal-VEE
05-14-07, 04:27 PM
Great writeup Feff.........and thanks for sharing your R&D work the fellowship :thumbsup:

type911
03-22-08, 07:36 PM
Too Funny, I installed My GC today. As I was tightening the last bolt on the install...The song came on the radio. I thought of the thread and had to laugh. Thanks for the write up.

Geof