View Full Version : Vibration at high speed...

07-28-2005, 03:22 AM
Only after I swapped in the 3.73 TC rear with discs, did my car start to vibrate at high speeds. Anything above 60-65 mph and the car has a consant vibration. If i remember correctly, it did the same thing when i had my 2.73s but only above 90mph. My '87 Turbo Coupe did the exact same thing from about 73-76 MPH then quieted down afterwards. I'm assuming it has something to do with things spinning faster at lower speeds...i.e. b/c of the 3.73 gears. But i'm wondering if any has had the same issues and if you were able to do anything to remedy the problem. The steering is not vibrating like worn brakes, nor is the handling affected. It is just a constant vibration. My rear view mirror vibrates so much it is hardly useful at night. I could live with it, I was just wondering what you guys thought. Thanks everyone.


07-28-2005, 06:16 AM
Check the alignment and balancing on your tires. Same thing happened to me, however when I got new wheels on it I got an alignment and got the tires balanced and the vibration issues disappeared.

07-28-2005, 06:31 AM
3.73 ... above 60-65
2.73s ... above 90mph.Same driveshaft?
25.6" tires (stockish)
3.73 @ 65 = 3200 rpm driveshaft
2.73 @ 90 = 3210 rpm driveshaft

'87 Turbo Coupe ... 73-763.45s?
3.45 @ 73 = 3300 rpm driveshaft

Either the driveshaft, or something nearby resonating at the same frequency?

07-28-2005, 02:44 PM
Thanks for the calculations. I will be getting new tires towards the end of summer and I was really thinking it might be the driveshaft. What can be done. It's the stock drive shaft. Balance it? Get an aluminum one? Thanks.


07-29-2005, 10:31 AM
I'de guess it's probibly your tires. I have 3.73s in my bird and I don't have a vibration issue and I still have the stock drive shaft as well with no special balancing.

07-29-2005, 04:56 PM
Well easy thing to do is take the drive shaft out and check the u joints.
Then u have the wheels to look at next.

Odds are its the drive shaft and the u joints need to be gressed

go six
07-30-2005, 06:07 PM
I had the same problem with my 85 Tbird. It was not an out of balance problem with the tires, had them checked at a couple different places. I had to change the drive shaft front yoke because it was somewhat worn (this shaft was originally off of a 68 mustang). The last I experienced a tire out of balance it basically shook the car. When the driveshaft was the issue is was more of a real fine vibration and it kind of pulsed, and like you said the mirrors were usless. But checking the tires is cheap and easy, and not a bad place to start. Hope you find it, If it is vibrating anything like mine was it can't be good for the rest of the drivetrain, engine, etc.

08-02-2005, 08:48 AM
If the problem was the tires/wheels it would still be doing it at the same speed(s). You have a driveline issue which was more or less proven by MasterBlaster. One possible problem not mentioned is a worn bushing in the tail housing of the tranny.

08-03-2005, 09:24 PM
I dont know if you still have all of these, but it might be worth looking at.

On the TC 8.8's there is a "dogbone" dampner that is bolted to the nose of the rear end. This is designed to be in sycn with a specific gear set, so a change could make it worthless. I had a cibration on my 88 TC with stock gears, and couldnt find it. I took the dogbone off in the interest of weight, and the vibration went away, and I have never missed it. Looking closely at it, the rubber hard hardened / deteriorated to the point it was a vibration rather than a dampner.

There is also a 5lb or so dampner on the crossmember on a TC, again, I removed mine and reduced a vibration in the shifter. Sme deal, the rubber was all hardened up.

I still have the big dampner on my tailshaft, and the doughnut on the front yoke of the driveshaft, but not for long ;)

I'm not sure what all models got these dampners, but at the age of all of the foxes, they are probably hosed anyway. It might be worth a look, just save them so they can be put back if something doesnt work out.

Bob Myers

08-04-2005, 11:16 AM
I'd also say check the yoke and the U-joint...

When you go from D to R (or R to D) with the brake applied, does it make a "Clunk"?
Or any other small noises?

Chuck W
08-04-2005, 12:10 PM
Replace the u-joints and have it balanced...

You'd have to have a custom one made if you wanted aluminum, or shorten some stock d/s (such as an Aerostar one).