I mentioned to my buddy (who is a mechanical engineer...unlike me) that I was considering taking the plunge for a light shaft for my '11 GT.

He shook his head and said that while there is a benefit to shedding the weight from the overall mass of the car, the actual rotating mass issue is overestimated because the diameter of the shaft is small enough that it makes little difference...as opposed to the rotating mass of your wheels/tires where the circumference is much greater so the mass imparts greater inertia on the system....so a shaft is probably not the best investment if all you're getting for your $700+ is a 20lb weight reduction.

This makes some sense but I'm not convinced since so many of you guys swear by them. Has anyone found any hard numbers that justify the price of the light weight driveshaft?

 

I initially thought I would do this mod, but have changed my mind due to reading on forums and asking questions of speed shops. The bottom line for me is that the cost of this mod does not justify the change in performance, there are better ways to spend your money for improved performance.
On the other hand, if you have the extra money go for it.

 

I'm pretty sure there are posts on here somewhere that show the aluminum driveshafts actually drop a couple tenths off your e.t. if you are drag racing.

 

Interesting...so you have heard similar feedback?

"A couple tenths" would be a huge improvement.
Can anyone verify?

 

Not only have I seen performance increases from people running a 1 piece driveshaft, but if your making big HP numbers and launch the car a bunch the 2 piece is prone to failure. A 1 piece DS is much stronger

 

Ok...are you sure the increases were isolated with the shaft being the only change?

What's the power limit on the stock driveshaft? I believe that it could be a weak point but other than that famous video of the wimpy V6 shaft letting go, I have never seen one fail.

 

1 piece Alum being stronger is about the only gain, and the extra NVH noise.
You wont see any ET improvement, its when you add multiple mods together along with driveshaft is when you will finally get some gains.

 

less vibration in the drivetrain

 

Well, you guys are saying opposite things here. IIRC, the reason that Ford uses a heavier/2-piece design to begin with is the goal of reduced NVH...but possibly only because this means of reducing NVH is cheaper than a precision/dynamically balanced one piece shaft.

So you both might be right.

 

Well, looks to me like another popular mod for these cars bites the dust.

 

I liked what mine did for my car. I did see an improvement in MPG's. I know that isn't the point of the shaft but I did notice an improvement. I also feel that it did make the car rev up quicker when running through the gears. I also seen a dyno where it freed up almost 14 hp. I will look for that dyno test results. It was on the net somewhere.

 

Well there should be some improvement thanks to a reduction in the amount of force lost to accelrating the mass of the components... I'd be totally surprised/thrilled if it was 14hp. I'd guess that it's much, much less than that.

If you do find that dyno chart, please share it. I suspect that there were other variables at work- change in temps, tune most likely...but it would be great to hear otherwise.

 

Personally saw it gain .08 on a tuned Coyote. Not quite worth a tenth in the quarter on that car.

 

not saying its true or I believe it but here is one
http://www.coastdriveline.com/PressR...DriveShaft.htm

here's another one with much worse results.
http://www.ws6.com/mod-1.htm

and one more
http://forums.nasioc.com/forums/show....php?t=2015402

there are more dynos charts on goolge image search

 

this ^

 

I've heard of the 2-piece DS eating itself in a bone stock car at anything over 100mph. In fact the folks at TwinTurbo50.com (John Lund/Jake Long/Ken Bjonnes) helped a BOSS owner attempt the texas mile while they were there testing their TT kit and she ended up chewing threw driveshafts left and right beyond 120mph. It's particularly bad with manuals.

The performance boost gained, which you can clearly see in the dynos posted by Glenn, is really just a bonus side-effect. Future-proofing against DS failure is the reason the part exists.

 

Sure you're not referring to the V6?

I can vouch my 08 factory piece didn't blow up at far higher speed. Can't speak for the 11-14 nor do I know if there were any changes for those year's V8's.

Failures of the factory drive shaft are not common in stock vehicles. At least on the V8's. The V6 is speed limited far lower than the V8. Keep in mind, owner mods - such as lowering - puts the risk on the owner, not Ford's engineers.

I've posted this several times concerning the factory 2 piece vs aluminum drive shaft, but I'll post this again for information purposes. From a Bullitt engineer that used to post here:


>>>>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 theclunk a bit easier to get. It is a trade-off - improved performance feel vs clunk.

>>>>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 isnot an issue unless the center bearing 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.

>>>>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!

 

Well I had the clunk and after installing the aluminium one piece 99% gone. After looking at the two piece I was happy I went with the replacement. NVH was slightly increased but I have an UCA and different transmission bushings that probably add.

 

Same here ...


First I will say it shouldn't be your first mod but it is worth it and would do it after suspension. You need an adjustable UCA on lowered cars.


MY 3.3 cent...

I had a 2/10ths improvement after installing but my comparison isn't scientific. It was the difference between 7-8 consistent 12.1s the previous year and 5-6 consistent 11.9s the following year but on older tires. These were my first runs each tine out. The runs were in similar very humid 90 degree weather. O'reilly is 800' ASL but the DA is usually north of 3300' ASL.

The times didn't matter as the overall driving was improved greatly. It removed the clunk sound and with quicker throttle response similar to an aluminum flywheel mod but not as light feeling. The best thing for me was the ultra light and effortless shifts in my MT82 further improving the shifting mods I had done. I can do fingertip shifts in all gears except reverse. It was the very first thing we noticed backing out of the shop and driving down the street. Maybe I had an unknown issue wth my OEM shaft...hard to say.

Getting the pinion angle just right can decrease or eliminate the NVH. I had my Nitto Nt05s rebalanced after the install and that helped take out a vibration. We noticed one of the wheels didn't feel right while on the dyno but with NT05s and super stiff springs you feel everything the car is doing, every line in the road.

Pinion angle on most lowered cars needs to be around -2 degrees or close to a straight shot from Trans to axel.

As of current vehicle setup I have no vibrations up to about 150 on a quick test. The Long Tubes and Nittos are loud at high RPM/Mph so it's hard to hear any other noise.

So take it FWIW.

Spring please come soon!

 

When I got my driveshaft I still had a clunk just not as loud. Then when I lowered the car the clunk is non existent. I did not get a new UCA when I lowered it either. Absolutely zero clunk now, strange.