So I have an issue I have been trying to track down for a few months now. I will try to describe a few different ways because one description could result in multiple solutions.

What I have done so far:
Changed sway end links all around MOOG
New sway bar bushings all around
Tie rods checked and greased
Wheel bearings checked
Front tires 5000 miles on them
Rear Nitto tires almost time to replace

What happens is when I am driving straight down the road and if I slightly and I mean slightly maybe a 1/2" turn right the car front end will move right and its very noticeable outside what turning the wheel a 1/2" would do, it actually moves the front end right significantly to almost be unsafe to drive. The same happens if I turn slightly to the left. If I take a curve at high speed I get a knocking/thumping noise however I think this may be related to the torque tube bearings.

Now IF the torque tube is the culprit and maybe the bearings are shot in it would that cause the symptoms above? I do have a clutch master cylinder going out that is on the table to be replaced. The thumping/knocking noise will subside if I clutch the car. It doesn't happen all the time though its intermittent and sometimes never presents itself during a drive.

I will upload the video of me driving with the noise present and you can tell when I clutch the car going 55mph down the road it goes away then comes back when released. Doing that now.

I may have a few issues going on that need some attention.

 

Also wanted to mention when inspecting the suspension thought I had found an issue when checking the sway bar brackets, passenger side was loose. So re-torqued it but problem didn't go away.

 

Sway bar bushings too tight.
Excess toe out.
Steering rack moving.

Any or all would do that.

 

Come to think of it, bushing being too tight could be it. I know I tightened the crap out of them. Plus I need to get a micrometer to measure the exact size of the sway bar, but just may end up replacing them as the rear sway bar did have some paint bubbling where the old bushing was.

 

Disconnect the end links. If you can move the bar up and down with them disconnected freely you're ok. Slight drag is expected. If it binds or you need to really work hard to move it then it cannot do it's job right. If it really binds then it loads up, snaps loose, loads up, snaps loos. Every time it unloads it jerks the car in an unpredictable fashion.

 

Hardest part has been finding the right bushings, stock 19mm Coupe 2000 rear is not what I have on the rear for the bar, not even close to fitting, need to break out the micrometer, but I do think the rear is way too tight. I'll make some changes this weekend if I have time and post the results, or this spring will just buy new sway bars and post results. thanks.

 

I doubt the swaybar would cause it to uncontrollable while driving down a highway unless the highway has terrible bumps. Something is loose or worn out. A loose cam bolt on a lower control arm can cause drivability issues too.

As for that noise, I'd say the torque tube and clutch needs to be looked at, and sooner than later.

 

So hey guys I finally had a chance to tear down my car. What I did for the maintenance. This fixed the knocking in the video above, also fixed the steering issue, the front coupler and pilot bearing were so worn the torque tube could snake back and forth.

Replaced these parts:
Pilot Bearing
Swapped stepped flywheel for flat flywheel
Installed new SPEC Stage 1 clutch
New slave cylinder w/TO bearing with speed bleeder line
New torque tube couplers
New torque tube bearings

I had to torque the pressure plate after installing the torque tube everything fit snug and nothing seemed loose, assembled great.

All of that has fixed the grinding I was getting launching from 1st gear or Reverse close to 1k RPMS

What I have left now is a knocking noise when turning a hard right turn. It feels like it is in the front suspension, when I had it down for maintenance I inspected all of that and didn't see any rubbing or notice anything loose. It is very subtle and almost hard to notice but I can tell its still there. Not sure where to look for it.

For anyone tearing out the driveline, inspect those couplers, if they are bad just change the bearings while you are in there, not hard just find a machine shop willing to press them out and back in. SKF bearings will work just fine. takes 3 bearings total. My bearings seemed to rotate fine, but once removed I could hear them rattling around inside. $50 for all three bearings

SKF 6007 2RSJEM SINGLE ROW BALL BRGS 1
SKF 6008 2RSJEM SINGLE ROW BALL BRGS 2

DO NOT use the Dorman couplers, I got the BMW style MADE IN GERMANY, believe they came from the same factory as the GM OEM ones, markings were similar to the stock couplers and marked Made In Germany
part number 26-11-1-225-624-M57 through pelicanparts.com $83 for 2 shipped.

Any ideas on that knocking noise, no where as bad as the video above, and seems to be different, also when I shot that video the sound was a bit off from actually riding in the car in person.

 

I'm just throwing this out there, and I have no clue if this could be the issue, but is it possible the top front shock mounts are loose?

 

I will take a look, it is very hard to pinpoint. I do know though from the pilot bearing to the rear is good to go. Torqued all bolts per the service manual specifications. Wish I could mount a camera somehow to watch the front suspension while driving.

 

I know you said you checked them but... A friend of mine had similar issue that ended up being the tie rod nuts were not torqued down to spec from the factory. Tightened the tie rod nuts and all problems went away.

Easy one to check if you have not already.


DJ

 

All the driveline maintenance has seemed to cure the problem, it no longer is there and the car is driving great. I noticed my Kooks headers were manufacture stamped 5/2012 so the LS6 engine was at least installed by that date or after. With the new driveline, sound motor, 2004 Transmission MN6 (19k when installed), car has 130k miles on it, I should have a lot of life in it and be good to go for another 100k easily.