Vibration

[mach14604]

I have a Vibration at 80mph and above. I have 18,000 miles on the car. Any advice to look at would be helpful.

 

[P49Y-CY]

first thing i would look at would be driveshaft indexing to pinion flange, and then i would check the pinion angle. try to drop the rear of the differential as much as possible for a better pinion angle. stock sucks. does the car have any irs mods?

 

[bubblehead93]

along the same lines, when did it start... did you have the driveshaft out prior to, if so, the shaft probably did not go back in indexed the same way it came out... correct that first... had a vibration not related to driveshaft indexing which was fixed when I replaced the transmission mount... failure was caused by my driveshaft actually being bent (early ford tsb on this if I recall)... doubt you have a bent driveshaft this many years done the road...

while fixing the pinion angle on these cars is a good thing to do, if it just started doing it, then pinion angle is likely not your problem... besides the driveshaft, any other work done before the vibration started...

 

[Huachipato]

Unbalanced tires? That is always my first guess.

I had a vibration that was "not as bad" after I tightened the rear wheel hub nuts.

 

[mach14604]

The car just had extensive work done to it. It now has a 2.9 Whipple, long tube headers, e85 conversion, Maximum Motorsports Subframe connecters, McCloud RXT clutch. The vibration comes through the steering wheel and no where else. I don't feel it anywhere else in the car other than the steering wheel. Car is not lowered and no IRS work was done.

 

[c6zhombre]

thats a lot of work done all at once. Under normal circumstances, I'd guess the tires need a good road force balance…but if you didn't have a vibration before those mods were installed…and you haven't changed anything related to the tires/rims….I'd start questioning the work that was recently done. Like what all was removed to get the clutch and headers in. Could be the d/s indexed improperly or possibly damaged mounts

 

[bubblehead93]

have to pull the driveshaft to do the clutch... I would still start there, eliminate the simple stuff first...

also, what was involved in the E85 conversion, did they need to drop the sub-frame for fuel line/filter access...

r/
Andy

 

[01yellercobra]

How close are the headers to the rag joint?

 

[Blueline]

- If you push the clutch in during the vibration does it go away?
- Steering wheel shake?
- Do you feel the vibration in the seat or your back?

My one cobra had a horrible shake at 80mph plus. The tires were new, previous owner installed them. I chased my tail and finally pulled all the wheels off and took them to get road force balanced at a top notch local shop. They found my new front tires had horrible flat spots and were no good. New front tires and no more problems. Just a thought.

 

[mach14604]

It is not a clutch or seat of the pants vibration( I know that much). Vibration all comes through steering wheel.

 

[Blueline]

It is not a clutch or seat of the pants vibration( I know that much). Vibration all comes through steering wheel.

Then really look at your front tires. Usually seat of the pants would be rear tires and or driveline. Have your front tires road forced balanced and tell them you have a bad vibration around 80. Easy thing to have checked and ruled out. Good luck, chasing vibes are never fun.

 

[CobraBob]

^^^ Best advice based on what was posted. Most definitely should be the first thing tried, and hopefully that will resolve the issue. If not, you need to focus on the front end suspension.