vib at 70

[SVTNICK]

Im having some problems. My Cobra is bone stock right now. for the last few weeks Ive noticed a vib coming through the steering wheel and I can see my radar shaking a bit when I hit 65 or above. I had the tires all rebalanced, and thought i had the problem solved...but it seems to have appeared again. (if it indeed had ever disappeared)Any ideas? Could it be the drive shaft? Wondering if anybaody else had this problem. Im taking the car to the dealer next week, so Im wondering if this is already a documented problem.

thanks
-Nick

 

[Lo Pony]

Very very common problem with the IRS and drivetrain in these cars. It's a total Pandora's box of possible causes, and possible cures. If it's recently appeared, you've either damaged the d.s. or the pinion bearing preload has dropped to the point that there's slop in the bearing.

Let me know if you want more info on how to approach this problem, since I'm designing a website specifically for people to tune the vibration out themselves at home. If you take it to the dealership, there's a TSB for the problem. They can try and follow the directions to tune the vibration out under warranty, but basically they have to balance/index the driveshaft ON THE CAR by trial and error until they can find an improvement.

 

[Vinnie T]

These are tough. It really depends on the type of vibration you are getting. If you are feeling it in the steering wheel, it just might still be the tires. Have them check to see if any are out of round or show any signs of internal belt problems.
Can you tell what frequency the vibration is? I mean, is it at the speed of the wheels or a much faster vibration more in line with the driveshaft? The driveshaft turns much faster, and will produce an undulating type vibration, where the tires are more of a shake. I had a driveline vibe in my 99, and it took Ford and the dealer several tries to get it right. It also involved combinations of 2 different trannys, 3 driveshafts (the last one pre- balanced to the tranny and diff as a matched set) , and 2 differentials before they found a combo that worked together well. Hope you don't run into this.
Good luck with it!

 

[Lo Pony]

Yeah, I forgot to ask you if it was a "hum" or airplane propeller type noise, or just a "shake", like you get with a tire. The two vibrations are totally different and it would be easy to tell one from the other, once you knew what driveline vibes are supposed to feel like.

 

[SVTNICK]

What Im going to do first is again get my tires balanced. Ill do that ASAP. Then Ill check to see if there is any difference before going to the dealer. I dont like this already. It is a shake that u can feel through the steering wheel and floor boards. No I hear no hum. Ill let you know what happens.

 

[Lo Pony]

It may very well be tires, then. Driveline vibrations are more of a hum or harmonic you can hear (sounds like a subwoofer).

Todd

 

[Vinnie T]

I agree with LoPony that it sounds more like a tire thing. Are these the OEM BFG's? If you rotate them, does the vibe change at all? Do any carry a lot of balancing weight, like the tire is somewhat out-of-round? Have a tire shop you can trust really check them out. You might even consider a shop that spin balances on the car.
The only other thing I can think of are warped rotors. Any shimmy while braking?

 

[SVTNICK]

yeah..they are the stock tires. But I did have them balanced a few weeks ago. Im going to check to see if any of the counter weights are missing. I origianlly thought it indeed was just the tires, until I came across the TSB about the vibes. Hopefully its just a weight missing. Suspension upgrades and gears are on hold until this problem is squared away.

 

[DamageInc]

Polished wheels?mark an index point on your tire!

I have a vibe/harmonic hum too. Now I can't say for sure that what I say is completely related to my problem and/or your problem but if you drive your car hard from time to time, grabbing gears to chirp the tires now and then, there is a very good possibility your wheels are slipping inside the tire. I mark my stock BFG's with a lumber crayon directly adjacent to the valve stem and I was suprised the first time I did this, the tire/wheel orientation has slipped at one point about 6 inches away from the original marking.

 

[Lo Pony]

I'm sure the tires do occasionally slip...I'm not too sure that some of the wheel balance issues with these cars don't have to do with unbalanced differentials and funky CV joints in the halfshafts.

And, just to clear the air a little, the original poster should recognize that it's not a VIB but a VIBE.

 

[SVTNICK]

LOL...yeah..its vibe..but i thought vib was our slang term..lol

 

[Lo Pony]

Nick, does your VIB get worse under acceleration? Like, if you're going 75 and no vibration, then you give it some gas and it starts shaking?

Cuz mine still does that too - in addition to the hum/propeller noise. I'm beginning to think it's in the halfshafts or differential balance.

Let me know.....about your VIB

 

[SVTNICK]

the vib i have progressively gets worse as you drive faster,,its not a horrible shake, but i can see(especially above 60) it get worse as I drive faster. I havnt been in the car for a few days, so I have yet to really listen to see if I have the hum..the car makes so many typical ford noises that I might of just tuned it out. I really hope its not the diff..i have 11000 miles on the bad boy and its not a year old yet....if it is a drive train issue my dealer is not going to like me.

-Nick

 

[Lo Pony]

If you had the hum (the drivetrain vibration) you would have noticed it by now. It would be like you were driving a prop-driven airplane down the road, or were sitting in the window seat by the engine on a DC-9 jet (voom, voom, voom voom).

I'm guessing what you have is more related to something at the wheel/tire level, or downstream of the pinion. Keep us informed. And pay close attention to the VIB - come back and give us a good description so we can recommend.

TF

 

[SVTNICK]

will do..getting tires rebalanced sometime this week..ill go from there again.

 

[SVTNICK]

phhheeeww

all that ranting for nothing. Took car to STS again for another wheel balance. Both the rear and left front out of whack...again!!!
I had them balance them 5 weeks ago. He said he could tell the tires had moved a bit in the rim, which sometimes causes the wheels to eventually become unbalanced. But to be sure I went on a banzai run down route 24 to make sure things were all good...and they were..thats a load of my mind....all that worry for nothing. I suspect that I messed up the balance while driving into Hoboken..no more of that...ill be taking the max from now on.

Man what a relief. You guys had me all paranoid.

thanks for the advice anyhow.

-Nick