I have noticed a *violent* vibration @ X>60mph.

You can feel it at any speed but it gets exponentially worse the faster you go, at below 60 you cant tell unless your looking for it, at 60 its just a slight vibration, but once you hit 80 the whole car is shaking violently.

I just purchased the car for a weekend toy and have a lot of plans for it, when I agreed to purchase the car it did not have this vibration, and I did not notice it when we drove to get the title transferred over.

Car is a 1999 Mustang GT w/ 124k.

Any help?

The vibration is:
1. Speed dependant.
2. Steering wheel is rock steady.
3. Feels like its coming from the rear.

 

check alignment

 

Will do once i can get the car into a shop, I never seem to think of the simple ****. Anything else it could be so I can check them all at once?

I was thinking the driveshaft could be slightly bent or a U-joint going bad.

 

Check the wheel balance. I remember I drove w/ ice still on my wheels and at 50 it was shaking like a ****.

 

Thanks for the suggestion.

I have four days off starting this Friday and will be going over every inch of that car.

Until then I have no choice but to drive it.
Hope nothing breaks.

 

more than likely a misballanced tire. A local shop shouldn't charge more than $40 to balance all 4 tires for you. It's prob not an alignment issue because the car would drift when you let go of the steering wheel.
This could also be a wheel hub bearing (more pricey) or front brake pulsation.
like i said though, almost 100% positve it's tire balance.

 

this happened to my friend, his rear axle was basically falling off, cost 1000 to repair..

 

This is very rare, but not impossible... more than likely its just tire balance.

 

Do you remember what was broken on your friends axle?

So that I can check just in case.

To recap (in order of priority):
Tires- Balance, Align, Check bearings.
Drivetrain- Check U-joints, axle mounting.

This really sucks, I literally have 6k that was on hold for a KB and supporting mods, that now has to be put on "hold" untill I can figure out what is wrong and fix it.

 

bent something... betting axle. BTW... make sure your driveshaft bolts are really tight... I had this a few times... once it was a single loose DS bolt. 12mm 12pt.

 

Ok, rebalanced the tires today, took it out on the autobahn and ran it up to 100 without any sign of a problem. Let off the accelerator and it started to vibrate again.

So... I learned two things about the vibration.

1. Its not the tire balance.
2. It only effects cruising and deceleration, when I accelerate it goes away for the most part.

 

drive shaft or u-joints. replace the u-joints and make sure the ds is tight (you may have to try replacing it)

 

Well I was planning to replace the driveshaft anyway...

Ordering an aluminum shaft from ford, should b here in a month.
(cant overnight to Germany)

 

ide start worryin about the joints and axle now

 

Well I am 90% certain that I found the culprit.

Ran the car over to the shop across the street at lunch today, put it up on the lift and...

Three of the four bolts on the driveshaft were very loose (finger loose).

Now just to wait for work to get over, and ill go take a run down the autobahn and see if the vibration comes back. If it doesn't, then the first wave of adders should get here in March.

 

I'd save the money for something else, you won't gain much from that upgrade.

 

I won't be ordering it if the vibration was fixed w/ tightening those bolts.
But if I have to replace the driveshaft I might as well do it right.

 

If it needs replacing, then go ahead, just if nothing's wrong w/ it, you aren't gaining anything.

 

Well, its fixed, ran it all the way to 140 and back down. It was solid the whole way.

Time to bring on the adders.

 

which base are you at? im thinking you bought a black 99 gt? there are so many mustangs out here that dont post on mighty so i could be wrong.

 

Yes, black 99 GT. Bone stock except for the exhaust.

 

Live on BFV, work on Taylor.

 

i helped a SFC drop a motor from his cobra last summer on taylor. i got too drunk with the guy that night i barley remember who he is.