Dan64456

Feels like its coming from the tranny or maybe even the drive shaft... It starts at around 67 MPH, and goes away at like 73, then comes back maybe at like 95 a bit more harsh...? It is right at the speed that I cruize at which is why it makes me wonder... Its by all means not harsh, but it is there... If someone could turn the radio down next time they are on a highway, and check for me if they feel it as well could you please let me know? Anyone know the cause or what I should do? Its not a big enough deal to flag the dealer about, but at the same time it sucks... Any suggestions greatly appreciated


-Dan

cortc

When did it start / Have you changed anything, new wheels etc...?

Dan64456

100% stock... 5 speed manual. 1700 miles. 2006 GT

underbird10

I have an '06 GT manual with 2200 mi. and I have something going on that may be identical to yours. Vibration starts at 68MPH and stops at just over 70MPH. It really feels more like a driveline vibration, not a tire. It's certainly not harsh, but you can feel it through the "seat of your pants". Feels to me like a driveshaft or possibly a rear-end gear issue. It's really more noticible when you are cruising or decelerating, not so much when accelerating.

What could it be? Time for a trip to the dealer?

UB10

Professor Wizard

It is.... perfectly normal for a factory car... it is Harmonics.

Factory drives trains, although "Balanced".. they re not truly balanced to a refined level like aftermarket or racing developed drive shafts. Same with the clutch and flywheels or factory torque converters.

So... you will pick up vibs at certain RPM's or speeds.

They won't hurt your car. they are just an annoyance!

They can be made to go away - - just pop for a high quality clutch, flywheel (or torque converter) and drive shaft .

underbird10

Okay, I'll buy the harmonic explanation... and if that is truely the case, I would guess it probably would happen at the multiples of that frequency (speed) also. Perhaps that's why it is happening for Dan at 97MPH as well, athough I haven't had mine up above 90 yet so I wouldn't know.

Is this a common problem on the Mustang, or is it isolated to a few specifics VIN's? I would assume, all things being equal, that there would be many '06 manual GT's that were built around March of '06 that were exhibiting this same behavior. Haven't heard this one before, but I had been planning to post this same issue for a couple of weeks.

Just to clarify, my car has a build date of March '06, it is a Perf. White GT coupe, all the options, no performance mods, 18" polished aliminum rims and BFG rubber.

I'd like to hear more from any '06 manual GT owners whose cars were built between Jan and May of '06.[sm=feedback.gif]

UB10

BLACK06GT4ME

I've exerienced the same thing with my 06 GT auto. It's more noticeable on concrete than asphalt to me. The harmonics theory is plausable, one of the more senior mechanics at my dealership told me about it when I had my first oil change. He said about 1 in 15 will experience it, most people don't notice it.

Stewart

I have the same thing. I had it before I replaced the gears and now I've replaced them with 4.10's it happens when accelerating through 1500 rpms, decellerating through 3000 and after about 75 mph when I decellerate it does it. I wouldn't care but when I hit 100 it feels like the car is going to rip itself apart. I don't care if they can't balance it perfectly, it is completely unacceptable that the driveshaft can't spin faster than what would be the equivalent of about 125 mph with stock gears. Ford even advertises the solild rear axle as being easier to replace gears. I'm taking mine in soon, I see it as a major safety hazard, especially since my driveshaft is spinning faster than it did with the stock gears. I have yet to drive a car where I feel driveshaft vibration like this, so I refuse to take as an inherent issue with cars.

Professor Wizard

Manifold, my Harmonics explanation is much more the plausible... it is fact.

Also... correct is that no two cars will have the same amount of vibs at the same RPMs. This is because of "Luck"... that the "Out of Balance" or out of round point will be at different position on every car due to the manufacturer techniques and quality control measures. Like no two wheels being out of balance in the same spot for example. Also, how much out of balance each part will be will vary from car to car.

You have 2 forces at work.. first is simply a straight forward out of balance situation - say on the drive shaft where you get vibrations, which usually get worse the faster the car goes. Usually if a single item is the cause the vibration outright, it gets worse as speed/rpm increases. Add to that, the balance forces of the clutch and flywheel, which when they get synchronized with the minute balance points from the drive shaft will "Harmonize" during those moments when the timing is correct for them to sync.

If you have a clutch, this can become more confusing because you can have a balance point on the clutch and one on the flywheel and when they are opposite each other it is smooth as silk, but when they align with each other it might sound like the transmission is going to jump right out of the car. Exactly when you get the vibrations is luck of the draw, dependent on when you engage the clutch.

Normally, the manufacturer specifications will keep the balance tight enough it would never be more then an annoyance. But sometimes, if ALL points in all parts are at the Maximum allowable, when they get harmonized you get a pretty hefty bonking going on under your car. – in which case you should visit the dealership because if it is that far off, it will eventually damage bearings and or mounts.

Dan64456

I am going to take a spin down 495 (the PA to DE 5 lane race track ) tonight and note the exact speeds from 0 - 140 where I feel it....