Does your IRS Cobra wag its tail under power?

[LaserSVT]

I wanted to get some more opinions on this before I go buy new tools that I cant reall afford right now if this is a seudo normal problem.
Do any of you guys get a tail wiggle under had acceleration? When im in 2,3 or 4th gear and at 70% throttle or more the cars tail wiggles left to right and back again mabey 3 or four times between 3K rpm and when I go shift at 6K. At first I thought it was the car searching for traction but I have tried it with the TC on as well and it still does it without turning on the "engauged" light on the cluster so the TC isnt kicking in. Since I have never had a car with this much power and an IRS I thought it was normal cause its done it since I have owned it and has never gotten any worse. I have driven 5000+ miles like this and hope I havent hurt her

The guys at SVTP told me that mabey my hub nut has loosened itself and may have caused dammage to the spline on the hubs Or it may just be loose and will be an easy fix. The whole thing is to me it just feels like bushing compliance On the picture I included I thought the bushings I circled in red would flex enough that I could move that tire a hair if I pushed on it but they said no.

How they had me test is was to get the rear in the air and grab the wheel at the 9 and 3 oclock position and try to wiggle it. It took all my strength but I can move it mabey 1mm total but it makes no noise and recenters itself when I back off on the force. I hope its just loose. Gonna see if my friend has the right size stuff at his shop tomorrow and will let me do it there I need a 36mm socket and a tq wrench that can go to 250ftlbs cause mine only goes to 180 or 200


So I guess my question is, does your Cobras do this as well? Have you had this issue and found it was a loose hub nut? Any input would be greatly appreciated

 

[COBRA90GT]

I've heard of a few other IRS cars doing this before. What type of tires (tread remaining?) are on the rear wheels and what kind of pavement was this happening on? Weather conditions?

 

[LaserSVT]

Dry conditions, it will do it on asphalt or cement, just not as pronounced on the cement. I have only pushed it like that once on the freeway so I guess I cant say for sure if there is a difference on different poad surfaces.
My tires have 5-6/32nds left and they did it when new as well. They are exactly 12" wide on the contact patch. They are PS2 295/30/19s.

I just got out from under the car and worked the hell out of that side to side movment and when I look straight at the upper bushing (the top red circle) while I wiggle the wheel I can see that upper control arm (?) does not wiggle as well. So my theroey of the bushing wiggling around is not the case and it seems that the nut might be loose. I guess I have to just wait till I can check it out at my friends shop tomorrow

 

[hotcobra03]

You might have a monday built car?i have heard that they put the wrong size bolts in the rear sub frame.on past post most have found the front are 2 small

 

[LaserSVT]

You might have a monday built car?i have heard that they put the wrong size bolts in the rear sub frame.on past post most have found the front are 2 small

Yes, I have the 12mm bolts in it still. I decided since the car has all the other suspension mods done I may as well finish it off with rear control arm bushings, IRS cradle derlin bushings and larger toe links. The car really only does the tail wiggle when I am passing someone. WOt while changing lanes with 12" wide tires and 450rwhp I guess will cause that.
Since my original post I have tromped on her several times on a smooth straight surface and she wont wiggle under thoes conditions. Its only under power when changing lanes that it does it
The new bushings should help out alot

 

[birdman941]

....................

 

[mustang50v8]

i am stirring up an old one here....


i also have the "wiggle" in the spring i think i am going to pull the bushings and put poly ones in there too as well as a poly diff mount. i will probably just go to maximum motorsports and pick several things out for it.

 

[Ben22]

yeah, mine does the same thing!

 

[mustang50v8]

sometimes, especially when its wet out it seems like there is a wheel that is loose back there, but i check it and find that nothing is loose, its only the rear end. so i know that its time to change the bushings out for poly ones....plus that will help me at the track with the wheel hop.

 

[Rad Ray]

It's the nature of the beast. I've replaced pretty much the entire rear subframe and adjoining parts, switched to symmetric tires etc. Best reduction came after replacing all of the bushings - did it myself and it was a real pita!. It still "kicks out" now and then. My track car (S2000) sticks like glue and believe it or not, having to learn how to handle the Terminator has made me better at the track.

 

[SVT32VDOHC]

I just picked up an 04 Cobra yesterday with 5,000 miles. I noticed this right away. Wet road, plus the road sucked as well. It did it on the freeway a couple times and scared the hell out of me. But once I got back to my side of town where thre freeway is better, it did NOT do it again. I guess I shouldn't worry about it.

 

[21MsclCr]

YES. Thats the only thing I personally dont like too much about the cobras. The IRS is great for the track and handling but too much power it just twists and you have to be careful no to do any harm. I doubt you will so you should be fine but yes it doesnt have the solid axle so it obviously will.

 

[SVT32VDOHC]

I would love to run a solid axle in my car, but the thought of tearing the IRS out on a 5,000 mile car just doesn't seem right. I want to leave it alone.

I love hammering on the Cobra's in 1st and 2nd, even with wheel spin, but I'm afraid I'll just hop.