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Steering Shake/Shudder

Believe I encountered some form of steering shudder at highway speed (75mph)....TC was on and steering fell was set to Sport. I have the full KB AGS-4 suspension under the car. Anyhow, the steering wheel started to vibrate accompanied with a very noticeable vibration felt throughout the car. Pushed in the clutch and coasted down to pull over...vibration did not decrease with speed. At about 10mph, the vibration quit like it was turned off with a switch. Checked everything...lug nuts were tight, no thrown weights, no play in front wheel bearing, nothing was broken or had come loose. Encountered the vibration once more at highway speed. Turned the TC off and set the steering feel to Normal....was fine for the remainder of the 700mile trip.

Any thoughts on if turning the TC off or setting the steering feel to normal was the solution?

Any other thoughts on things to look at?

What is the difference between the M-3200-EPAS steering rack and the stock Boss rack? Are there other parts that need to be installed with it (ABS module?)?

Any other Boss guys that has modified their front suspensions (bushings, bump steer kits) who have encountered steering shudder? Understand this is common with the GT guys.

Thanks
r
Eric
 
I believe you have to do some welding in order to install the KB front LCA's. Did you check the welds?
 
Rick,

No welding required to install the KB front LCAs or K-member. I will check all the torques and components. The shudder occurred around 100 miles into the 700 mile trip....had been at 75mph for 20-30 min. After turning off the TC and setting the steering feel to normal, the shudder never came back. The KB suspension runs 9deg of positive caster and the bushings are poly....also have a MM Bump Steer Kit installed. The shudder certainly got your attention...

There must be some sort of feedback loop as the GT guys have experienced this when they tighten the front suspension up...?

Eric
 
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GA
I read somewhere on either here or S197forum that the street 11+ GT EPAS can get thrown into a feedback loop at certain speeds when you change the suspension geometry and causes the shake/shudder that you are talking about. The Boss 302S steering rack does not have the offending firmware. You cannot update the stock rack firmware so you have to replace the rack with the 302S unit (around a grand). I don't know if the street Bosses have the same EPAS firmware as the GT - you would have to research this.
 

PeteInCT

#LS-378 - So many Porsche's, so little time....
Moderator
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Connecticut
PJWANNABE said:
I read somewhere on either here or S197forum that the street 11+ GT EPAS can get thrown into a feedback loop at certain speeds when you change the suspension geometry and causes the shake/shudder that you are talking about. The Boss 302S steering rack does not have the offending firmware. You cannot update the stock rack firmware so you have to replace the rack with the 302S unit (around a grand). I don't know if the street Bosses have the same EPAS firmware as the GT - you would have to research this.

The Boss 302 does not have that issue, but the GT's do.

-Pete
 

Grant 302

basic and well known psychic
The 'known' problem is with Active Nibble Control in all of the 2011 EPAS racks.

It is possible that with the full KB front setup, that the increased stiffness and revised geometry could upset a '12+ rack.
 
Talk with the gang at Vorshlag. They had a similar problem (well documented on their website) with their 2011 GT track car after upgrading the front suspension components. It's my understanding they upgraded to a Boss 302S steering rack to fix the problem. It is unexplainable to me how companies sell suspension kits, but fail to address known problems. I'd give KB a call as well; if their components cause the problem it seems they should have a fix; at least if they want repeat business.
 

Grant 302

basic and well known psychic
HackBoss302 said:
Talk with the gang at Vorshlag. They had a similar problem (well documented on their website) with their 2011 GT track car after upgrading the front suspension components. It's my understanding they upgraded to a Boss 302S steering rack to fix the problem. It is unexplainable to me how companies sell suspension kits, but fail to address known problems. I'd give KB a call as well; if their components cause the problem it seems they should have a fix; at least if they want repeat business.

I wouldn't be so harsh about parts that have been in development for the whole S197 platform. In aftermarket terms, the problem is relatively new. Sometimes it takes some time to shake out quality issues like neema and Chris have with the relatively new Steeda X-11 balljoints.

I'd give KB a call first.
 
Spoke with KB and Rehagen...though uncommon, they both had heard of Boss cars having the shudder issue after doing work on the front suspension. On their advice I replaced the Boss rack with the Ford Racing M-3200-EPAS rack. Its a bolt-in mod....no reprogramming required. I've put another 1000 miles on the car since replacing the rack....no sign of any shudder or shimmy. So, though rare on Boss cars, in my case I'd say the cause of the shudder was the Boss steering rack.

Butler MacMaster Performance (www.butler-macmaster.com) had a sale going....$850.

Eric
 
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I had to replace my 2011 GT rack with one out of a 2013 GT after installing Prophane front control arm bushing. I haven't had the issue since.
 
I've had this issue with my 13 Boss as well exactly as what OP described. The dealership was of no help and continue to tell me it's normal. It's not bad enough for me to spend nearly $1000 on a new rack to fix, but it is annoying non-the-less.

All I have done that affects the front suspension is the Steeda Boss specific springs. These don't change the geometry much if at all, but they are a stiffer spring rate.

Grant, do you think the springs could really cause this even though the alignment is good and the ride height hasn't really changed?
 

Grant 302

basic and well known psychic
I really doubt the spring rate would do it, but that only leaves the change in ride height geometry. Haven't ever heard of that being a problem before and just seems unlikely for a mild drop.

I think I'd try to get it pushed up to Ford Customer Service via Deysha on the Mustang Source...if you can't get any further with your dealer. She's been able to help when dealers can't or don't.
 
WorldFamousZ said:
I've had this issue with my 13 Boss as well exactly as what OP described. The dealership was of no help and continue to tell me it's normal. It's not bad enough for me to spend nearly $1000 on a new rack to fix, but it is annoying non-the-less.

All I have done that affects the front suspension is the Steeda Boss specific springs. These don't change the geometry much if at all, but they are a stiffer spring rate.

Grant, do you think the springs could really cause this even though the alignment is good and the ride height hasn't really changed?
I just started getting a vibration around 60 that seems to go away above that. Have you recently had your wheels balanced, I am wondering if that is my issue.
 

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