Earlsays

I have noticed in my 2014 GT / 6R80 there is a bit of a delay upon take off and it will make a "clunk" type sound as it engages and takes off, almost feels like a loose U JOINT would feel - is this a torque converter lockup schedule issue? Is this a two piece drive shaft issue?

Occasionally when driving around town slowly it will do this as well...stock tuning issue?

Or is this some other problem? Car is all stock 2014 GT / 6R80 / 3.15 gears, 6,000 miles

done it since day one.

Horspla

The things you describe sound very normal for these cars Mine included). The clunk is slop in the driveline and the delay feeling you're getting is from the stock tune. Both can be addressed by the aftermarket and neither will be taken care of by Ford! An aluminum one piece drive shaft and a good modest tune from a trusted source will get you where you want to be.

John

CriticalmassGT

Odd, because I have neither issue. I'd have them check it out. If I had a clunk going on, it would drive me nuts. Same tranny and gears as yours. 5.0 GT Premium with the Brembo package, 2014 with 3k miles

FordService

Hello Earlsays,

If you haven’t already, I recommend you get it checked out at your Ford Dealer to make sure there’s nothing else going on. Let me know what they say.

Deysha

choate

2 piece drive shaft engaging. Normal. Mine does it too but not all the time. It's just certain ways of taking off that makes it happen

Earlsays

I figured. Does the two piece drive shaft have a center U joint? Is one piece moving independent from the other ever so slightly, allowing this condition?

Will I see a significant improvement with the addition of a single piece drive shaft, while making NO other changes?

det97

The clunk happens in the V6 too. A tune after a dealer visit is what I would do.

choate

It's a matter of opinion. It's not worth 7 or 8 hundred dollars to me. Here is how it's made and how to install one if you wanted. I assume it's still the same but maybe not. The noise is just a noise of it coming together. It allows movement. Does yours do it all the time? Mine rarely does

http://www.cherod.com/mustang/HowTo/...riveshaft.html

cdynaco

There is no roll in of the 2pc factory driveshaft unless yours is defective. That's just an uninformed rumor on forums.
What you are hearing is driveline lash... taking up slack be it in your Traction-Lock diff and your trans. Is this the first time you've owned a Traction-Lock? They are not noise free.
Since you have auto's, you can't minimize it with better clutch/throttle work. A number of guys that went to the 1pc still report noise when they aren't shifting smoothly.

From a Ford engineer on Bullitt that used to post here:

s>>>>
Clunk is driven by total driveline lash, dominated by the gear sets and clutch tuning/capability. The 3.73 amplifies this a bit compared to the 3.31 and 3.55 axles. The 2-piece driveshaft is not the cause of the clunk noise. The Bullitt will have higher levels of clunk compared to the base GT. The base GT throttle response is a bit softer than the Bullitt's. The increased throttle response makes the clunk a bit easier to get. It is a trade-off - improved performance feel vs clunk.

s>>>>

I don't recalling "dis"ing anyones products. It's up to you to believe what you want. Whatever criteria you have for something being superior or inferior may not match mine or others. I've met Gary Patterson- he's a nice guy.... I'm just here to answer questions and try to be of help.

The post mentions high speed and 160mph - The Mustang (as it leaves AAI) is speed limited well below that for a reason. Like I said before, I do not know specifics about the dynotech piece, what it does or does not do.
I do know about the 2-piece in the factory car. It is a fairly robust piece. Vibration is not an issue unless the centerbearing shims are not installed properly, the shaft has a balance issue or the pinion angle is off. These would be quality issues (that I'm not aware of having in production), not design. The 2-pc has no roll in whether or not you have a random vibration. U-joint angles, run-out (flange or shaft), balance and system modal (resonance) response govern vibration.

s>>>> 2 piece drive shaft

The 2-piece driveshaft is required to meet internal engineering requirements for safe operation at max vehicle speed. Basically, it is designed to provide a driveline system resonance well above what the speed limiter will allow you to operate at. If you put your driveline into resonance, bad things may happen! I've seen what it does to a car and it isn't pretty.

The driveshaft CV joints are required components on this type of driveshaft when combined with a live axle. If the rear suspension were IRS, simple flex couplings would be used (look at the new Camaro, Challenger, etc...) and would make for a lighter driveshaft.

The driveshaft also has an internal torsional damper (ITD) which is soley there to attenuate axle whine. If package allowed, the ITD would be mounted on the exterior of the driveshaft as a much lighter ring design. Since the equivalent inertia is required out of the smaller diameter part when installed inside the driveshaft, the mass has to increase. So, you get a heavier ITD vs a lightweight ETD.

A single piece steel or aluminum 1-piece would have to be larger in diameter than the current package allows. Basically, you would have contact with the fuel tank at full rear suspension jounce. 1-piece carbon fiber was explored at one time...

Hope this helps.


I would not assume an aftermarket piece "solves" a problem. Yes, you can stuff a massive driveshaft into the tunnel but it will not meet standard vehicle engineering requirements. Our requirements take many factors into account, with the biggest one being your personal safety under a wide variety of operating conditions. Our parts are engineered to work in one big system. Aftermarket parts are generally not engineered. By this, I mean that they are designed to fit properly (usually) and improve one or two attributes specific to your application.

For example, if you want a lighter weight driveshaft that gives you less rotating inertia, you can buy this aluminum 1-pc driveshaft. But, that's all you get - lighter weight. Not proven durability, safety (how does the driveshaft react in a rear impact?, clearance to other parts like the fuel tank?), NVH, ride (driveshaft plunge force actually affects your ride quality), etc...

But that's the great part about it being your car. You get to decide what you want your Mustang to be. Just be cautious and think about how these parts may affect the rest of your driving experience, safety and wallet if it breaks or breaks something else in the car.

I've been in your shoes (which is why I became an engineer and worked my way onto the Mustang team!) and know exactly where you are coming from, though. I don't know specifics about the d/s you are referring to but I'm just giving you some things to think about and consider.

Thanks for buying a Bullitt!

And this link is laughable. First off, a driveshaft doesn't give you HP.

choate

Maybe his wording is bad but it should free up lost horsepower shouldn't it? Stage3 says in their description for a 13-14 GT500 it frees up 14 wheel hp.

http://www.stage3motorsports.com/201...riveshaft.html

cdynaco

Yes you are stating it correctly. Similar to underdrive pulley's... you are reducing drag on flywheel HP to the rear wheels.

Earlsays

That was an extremely interesting bit of reading...thanks for re-posting!