Bad vibration....from somewhere.

[quik cobra]

First off the vibration doesn't even start until about 120mph (I know, I know) but gets worse as I go past that. I'm not one of the guys that does the runs up to 160 or anything but sometimes she needs to be opened up on some of these backroads.

So first thing when I first start driving the car in the morning I feel like a slight "wobble" at low speeds (5-10 mph) but it quickly goes away and there is no more "wobble", fast forward to finding a nice stretch of road and run it up to the top of third and into 4th hit 120 and it feels like the car is going to shake apart.

I'm not even sure this belongs in this area but I figured it was start.

Trans is stock except for Spec 3
driveshaft is stock
Detroit Tru-Trac Differential with 3.55’s

Just for the sake of maybe being suspension

MM (Maximum Motorsports) Caster/Camber plates.
MM Strut tower brace and k-member brace.
MM Grip kit for rear diff with all new bushings.
MM IRS Adjustable Tie rod kit and Adjustable Sway-bar end links.
IRS Diff bushing kit aluminum.
MM Adjustable Coil-overs shocks front and rear.
Has weld and bolt-in sub-frame connectors.

Any help or ideas would be appreciated. Need anymore info I'll do my best.

 

[DSGNator]

I just got through chasing down a vibration in my Cobra. I don't know if it was there at 120mph, I haven't got to any of those backroads just yet. Only had the Cobra for a couple weeks. My vibration would just come and go at almost any speed. Sometimes it was there sometimes it wasn't. I figured I just needed to get my tires rebalanced. When I took it in for that, the mechanic brought to my attention that my front wheel bearings were bad. He didn't want to chase a balance issue with the bearings allowing my front wheels to wobble. They didn't have a very significant amount of play in them, but it was definitely enough to cause these annoying vibrations. In theory, swapping out the bearing/hub assembly is very easy. There are multiple write ups on the forums here. But in my case the inner cone of the wheel bearing seized up on the spindle So I had to cut, hammer, and torch mine to remove them. But most people say they just slide right off. Anyway, replacing the bearings/hubs made a world of difference. It honestly feels like I'm driving a new car now. I'd look into this if you haven't already, apparently the factory bearings are notorious for going bad in our cars.

 

[R.D.P.]

I just got through chasing down a vibration in my Cobra. I don't know if it was there at 120mph, I haven't got to any of those backroads just yet. Only had the Cobra for a couple weeks. My vibration would just come and go at almost any speed. Sometimes it was there sometimes it wasn't. I figured I just needed to get my tires rebalanced. When I took it in for that, the mechanic brought to my attention that my front wheel bearings were bad. He didn't want to chase a balance issue with the bearings allowing my front wheels to wobble. They didn't have a very significant amount of play in them, but it was definitely enough to cause these annoying vibrations. In theory, swapping out the bearing/hub assembly is very easy. There are multiple write ups on the forums here. But in my case the inner cone of the wheel bearing seized up on the spindle So I had to cut, hammer, and torch mine to remove them. But most people say they just slide right off. Anyway, replacing the bearings/hubs made a world of difference. It honestly feels like I'm driving a new car now. I'd look into this if you haven't already, apparently the factory bearings are notorious for going bad in our cars.

Interesting - I assume you could feel it through the steering wheel? I have a slight vibration from about 40-70mph that I'm about 95% is my driveshaft.

 

[quik cobra]

My first thought was the drive shaft but I would have guessed it start to vibrate before 120. I also thought it might be the wheel bearings but when I did my brakes this last weekend I checked to see if the fronts had any play in them and they seemed tight with no play at all. I just put new tires 5000 miles ago and the vibration was there before that. Maybe I should look at little more into that. I'm guessing there is no way to tell if the drive shaft is out of balance while still on the car?

 

[DSGNator]

Interesting - I assume you could feel it through the steering wheel? I have a slight vibration from about 40-70mph that I'm about 95% is my driveshaft.

My vibration was primarily in the steering wheel at various speeds. But it shook bad enough at times that you could feel it throughout the entire car. It very well could be a drive shaft issue, but that's something I never really heard of before owning this car. I've read about several Cobra owners getting there's re-balanced to correct vibration issues. It just seems odd to me that a drive shaft could just become unbalanced. But I guess in theory any rotating mass can become unbalanced. I don't think you can test the balance while it's still on the car, but I could be wrong as this is something I've never done or had done.