Recently while cruising at speeds up to about 50 or so I'm noticing a whistling sound from the car, bounces off whatever i might be driving next to so i'm pretty sure it's coming from under the car.

Anybody else with 1-piece driveshaft notice this?

I tried making a video but it got drowned out by my exhaust.

 

alls I can suggest is take a look under there and see what you can see.

 

That may be the increase in drive train noise that comes with it, is it similar to the gear whine from the rear?

 

Similar, yeah ... almost sounds like a backing plate rubbing against a rotor ... weird ...

Gonna have the car back up on a lift again soon to rotate the driveshaft another turn, gonna check a few things while I'm under there.
I also want to install a safety loop.

 

Not sure really what your hearing but I had a sound at one point that was really metallic sounding that I also thought was from under the car then I pin pointed it to the front and found it was a rock lodged against the rotor. so when you mentioned the rotor this came to mind. Take a look but maybe not

 

put the rear axle on jack stands and put it in gear/drive. You should be able to pinpoint the noise then. Be SUPER careful doing this though. Use wheel chocks for the front tires if u got 'em

 

What brand driveshaft? There are some with CV joints that are not as picky on the pinion angle. With the Track Pack it also might make more noise because of the torsen differential. Still I would check it out.

 

DSS driveshaft

 

Could also fold down or remove the back seats to see if you hear it more near the back, meaning it's the diff. Several guys on BMO said their whine got louder after 1-piece installs.

 

Well... just be thankful it doesn't sound like bongo's.

 

My bet it's the rear axle. I have noticeable gear whine from my Torsen diff too. You can hear it easily at ~72 mph in 6th gear on the highway. But I have also noticed this in either 4th or 5th at lower speed, but higher RPMs. It all depends on the road and your driving style.

I can also tell you that the DSS shaft didn't cause this, but just made it more noticeable. I had the gear whine on the stock shaft and noticed it as well after my DSS install, however the audible pitch of the gear whine was now higher.

 

Yeah, I had the Torsen whine and it got louder after the install of the BMR tubular LCA's.
At 10k miles I changed out the rear diff fluid and trans fluid and the highway-speed whine is now no longer there, I'm now at 13.5k miles and I don't think I've heard it for at least 1k miles.
But this whistling I hear at 20+ mph and by the time I get to 50-60 I don't hear it anymore, but at those speeds I also don't tend to have anything next to me for the noise to bounce off of.

I'm once again thinking of putting the stock d/s back in to see how my noises/vibrations change

 

You have to drop the exhaust for the install correct? If so it may be that it is an exhaust leak. I had something similar when I switched my cat-back and I would hear a wooshing noise only near cars and when going past dividers. A local exhaust shop checked for leaks and said there were none but the cats could have been making more noise as they were flowing more. Maybe that is what the whistling is.

 

Did you have any clunk from the two piece? I have had one since day one and unless you shift perfect you will hear it. Its also better shifting 3k or above. I am going to check to everything is tight as some say it is the sway bar bushings and others say it is the lash of the gears. I can feel it about mid way between the trans and differential. I hear no gear wine even though I have a better UCA. I think the 3.73 and higher ratio's tend to be more noisy and must be set up perfectly. I will go for a one piece if it gets rid of this clunk.

 

Yes, I had clunk from the OEM shaft. However, you have to know that the factory design does hide/mask some transitional torque transfer at low speeds.

It all depends upon how smooth your shifting style is between gears on various roads. I get 'smaller' clunking now that the driveshaft is more solidly connected to the other ends of the drive train. I tend to keep the revs down and not always keep torque applied with my right foot. But now that I have noticed the minor clunk, I'm trying to shift accordingly to a avoid this because it just sounds/feels like "You're doing it wrong"

 

You have vibrations too? What sort of vibrations and at what speeds? Have you tried reindexing the shaft?

 

They start at about 95 and it feels like it's coming through the floorpan, not a front-end wobble which would make the steering wheel shake

 

I PMed Gabe about this - but I just installed the same unit myself today. Ran up to 115 with no noticeable vibration. Hand on the shifter and very little vibration coming up through the transmission. Much quieter than stock.

I think Gabe may have gotten a defective piece. Hopefully DSS will take care of him.

Also - shout out to Jay@Hypermotive for shipping mine to an APO. Thanks!

 

Here is a quote from a guy on allfordmustangs forum; seems he found the original Ford factory unit best with a lengthy story / explanation. What do you think?

As most of you know I have been through hell and back trying to get my driveshaft working in my car without vibration over 150mph. At some point this fall I plan on going 200mph. Obviously a vibrating driveshaft is not part of the plan.

At first, obviously I thought there was something wrong with the shaft, so I had it balanced. It still vibrated but now at a higher speed (it was vibrating about 110mph). Then I thought that I had my driveline angle set up incorrectly. I then set forth to learn everything that I could about driveline angles, why you set them up some ways, etc. I ended up setting the driveline angle up the three possible ways that a S197 can be set up at (with an adjustable UCA) and in each instance it still vibrated but at different speeds. I did get it to about 135mph before it started to vibrate though.

At that point I was stumped, I was looking for other problems that the car may have had, but eliminated them and they did not affect the car. I was lucky enough to be contacted by one of the other driveshaft manufacturers (Shaftmasters) and they offered me the opportunity to bring my shaft down to there shop (can you believe we got this far without a “shaft” joke?). They were incredibly helpful and we disassembled the entire shaft and “blueprinted” everything as we put it back together. Then they checked it for run out which was absolute zero, I was surprised, I expected it to be out at least a thou or two. Then they high speed balanced it for me, and I mean HIGH SPEED. When all was said and done the driveshaft was never going to be anymore perfect. I am very good with all things mechanical and they allowed me to hang out with them while they worked on the shaft. I assure you no step was skipped, half done, etc. They threw everything they had at it.

For all intents and purposes the shaft is perfect. It has been checked and assembled at a level that no production driveshaft is.

Once I got it back in the car and set it up with “opposing” yoke angles (equal at both ends to cancel each others vibration out) it was immediately a lot better. I could get the car up to 150mph before it started to vibrate, and even when it did start to vibrate it was much less violent. It went way up in MPH and went from scary vibration to annoying vibration, but still not perfect and not something that I wanted to go 200mph with.

I then started to do a lot more research, I talked to FR500 guys, Miller Cup guys, the Griggs Racing guys, the guys who built the 250mph Mustang that was on the cover of Hot Rod a few months back and lucked out and one of my customers ends up being a driveline, and specifically a driveshaft engineer.

The bottom line is that the S197 chassis doesn’t like lightweight (this is key) one piece driveshafts. Go figure right? Ford didn’t put 2 piece shafts in them because they were cheaper than one piece shafts. The S197 chassis has an inherent harmonics issue when it comes to the driveline. This driveline harmonics issue is also the reason the OEM Panhard rods are filled with lead shot or whatever is I there to make them weigh a ton. From what I learned Ford had to jump through a lot of hoops to get them to not vibrate on the production cars. Everything about the driveline effects it’s propensity to vibrate in one way or another. Flywheel, Clutch, rear end ratio, type of diff, axles, wheel diameter, width and weight, control arm material and design, bushing materials, pretty much everything you can think that relates to the driveline. Well all of the above on my car is aftermarket. One combination of parts can make it worse, one combination can get you a “net zero” compared to OEM and unlikely another combination could make it better. Mixing and matching parts in attempt to eliminate the vibration issues could possibly take the rest of eternity or be impossible to do with stiff, strong and light high performance parts.

Most of the people I talked to were amazed that I got the vibration issues down as far as I did using the collection of parts I have I the car.

In a last ditch effort I put another manufacturers (not Shaftmasters) shaft in the car just to make sure I was still not dealing with the shaft. Well, that one vibrated too, but at a lower MPH than the Powerhouse (probably because the Powerhouse had been put together so well). At that point I figured I would do what it is always best to do and that was to go back to basics. I put the OEM shaft back in, set the pinion angle at -1 deg in relation to the shaft and then took it out for a test drive. It was smooth as glass all the way up to 175mph and I got my own personal best top speed out of it and that was with backing down because I thought the hood was going to come off. I did have the windows down and my big fat, heavy, cheap/junk Chinese wheels made for some “Not pool table smooth” feelings with the car but I no longer had any of the driveline vibration/harmonics I had before.

Clearly if one wants to go stupid fast with a lightweight one piece driveshaft they are going to have to do a whole lot of driveline R&D to make it work. And according to some very smart people I talked to it would probably be impossible to do it without using some very high dollar CV joints instead of the U-joints that all the aftermarket S197 lightweight shafts come with.

Through out this process I have leaned a lot more than I wanted to when it comes to setting up driveline angles on the S197. And I can tell you some of the links I have seen to instructions on how to set them up are dead wrong or misleading at best. I may put together my own write-up but I am slammed working on my site right now so I don’t have the time. If you are having issues feel free to PM me though. There are about a million variables that crop up when trying to set the angles. Not accounting for these will skew your results dramatically. Something as simple as how the car is jacked up and supported will change your results dramatically.

Needless to say I am selling the Powerhouse shaft. It does not suit my needs unfortunately. I have placed an ad in the classifieds section. If you are interested check the AD out before PM’ing me please.

 

a brief explanation of forced harmonic vibration as well all systems have a natural frequency. I had to learn all this shizz and it is real. Hope you enjoy the read as much as I do:

Forced Harmonic Vibration
Harmonic excitation is often encountered in engineering systems. It is commonly produced by the unbalance in rotating machinery. Although pure harmonic excitation is less likely to occur than periodic or other types of excitation, understanding the behavior of a system undergoing harmonic excitation is essential in order to comprehend how the system will respond to more general types of excitation. Harmonic excitation may be in the form of a force or displacement of some point in the system.
We will first consider a single DOF system with viscous damping, excited by a harmonic force , as shown in Fig. 7. Its differential equation of motion is found from the free-body diagram.
(29)

Figure 7 Viscously Damped System with Harmonic Excitation



The solution to this equation consists of two parts, the complementary function, which is the solution of the homogeneous equation, and the particular integral. The complementary function. in this case, is a damped free vibration.
The particular solution to the preceding equation is a steady-state oscillation of the same frequency w as that of the excitation. We can assume the particular solution to be of the form :
(30)
where X is the amplitude of oscillation and f is the phase of the displacement with respect to the exciting force.
The amplitude and phase in the previous equation are found by substituting Eqn. (30) into the differential equation (29). Remembering that in harmonic motion the phases of the velocity and acceleration are ahead of the displacement by 90° and 180°, respectively, the terms of the differential equation can also be displayed graphically, as in Fig. 8.

Figure 8 Vector Relationship for Forced Vibration with Damping



It is easily seen from this diagram that
(31)
and
(32)
We now express Eqs (31) and (32) in non-dimensional term that enables a concise graphical presentation of these results. Dividing the numerator and denominator of Eqs. (31) and (32) by k, we obtain :
(33)
and
(34)
These equations can be further expressed in terms of the following quantities:



The non-dimensional expressions for the amplitude and phase then become
(35)
and
(36)

These equations indicate that the non dimensional amplitude , and the phase f are functions only of the frequency ratio , and the damping factor z and can be plotted as shown in Fig 9.


Figure 9 Plot of Eqs. (35) and (36)

Equation of Motion : Natural Frequency
Figure 2 shows a simple undamped spring-mass system, which is assumed to move only along the vertical direction. It has one degree of freedom (DOF), because its motion is described by a single coordinate x.
When placed into motion, oscillation will take place at the natural frequency fn which is a property of the system. We now examine some of the basic concepts associated with the free vibration of systems with one degree of freedom.

Figure 2 Spring-Mass System and Free-Body Diagram


Newton's second law is the first basis for examining the motion of the system. As shown in Fig. 2 the deformation of the spring in the static equilibrium position is D , and the spring force kD is equal to the gravitational force w acting on mass m
(5)
By measuring the displacement x from the static equilibrium position, the forces acting on m are and w. With x chosen to be positive in the downward direction, all quantities - force, velocity, and acceleration are also positive in the downward direction.
We now apply Newton's second law of motion to the mass m :

and because kD = w, we obtain :
(6)
It is evident that the choice of the static equilibrium position as reference for x has eliminated w, the force due to gravity, and the static spring force kD from the equation of motion, and the resultant force on m is simply the spring force due to the displacement x.
By defining the circular frequency w n by the equation
(7)

Eq. 6 can be written as
(8)
and we conclude that the motion is harmonic. Equation (8), a homogeneous second order linear differential equation, has the following general solution :
(9)
where A and B are the two necessary constants. These constants are evaluated from initial conditions , and Eq. (9) can be shown to reduce to
(10)
The natural period of the oscillation is established from , or
(11)
and the natural frequency is
(12)
These quantities can be expressed in terms of the static deflection D by observing Eq. (5), . Thus, Eq. (12) can be expressed in terms of the static deflection D as
(13)
Note that , depend only on the mass and stiffness of the system, which are properties of the system.