East87

Well I have something of a verdict from my test drive tonight. With my dad and brother in the car (an extra ~320 lbs combined), I took it up to about 115 and the vibrations were markedly subdued. Car felt more solid than during the first test drive, and heavy braking at high speeds yielded dramatically reduced vibrations. However, the shuddering was still generated in the same way as during my initial test drive (high speed, then deceleration/braking).

I then took it out myself. The reduction in weight resulted in more noticeable noise and shuddering. I felt the same harsh vibrations to a bit of a lesser degree, but the range of speed where they occurred shifted much, much higher. The car doesn't start vibrating at acceleration until around 115, vibration on deceleration were mild at those speeds, but grew in intensity as i decelerated from the mid 120's. Heavy bursts of braking from 125 resulted in the same old vibration (about 10% reduced maybe?) (but I was scared to take the car up to 125 during my first test drive...), and by the time the car slowed to 110, the vibrations were dramatically reduced or completely gone.

Overall, I had more confidence going into this test. The driveline felt even more solid than during my first test drive, and the bucking and shuddering at 85-105 is pretty much gone. However, as speed increases beyond that point, vibrations become present and noticeable.

At best, 0-110 is pretty much perfect. 110-120 accelerating and decelerating/braking is relatively mild. It gets pretty ugly as you decelerate and brake from 125+.

I have no idea why the combination of speed, weight, and decelerating/braking is causing the noise and vibrations heard and felt throughout the car... Maybe someone can enlighten me.

I wonder how hard it would be for me to find my pinion angle. Any thoughts?

jahudso2

Vibrations are noticeable when a forcing function frequency matches the natural frequency of a part or your entire vehicle. The forcing function frequency is the speed of your driveshaft which varies with vehicle speed. The natural frequency is a function of mass and spring constant. Therefore, as you change the weight of an object, then the natural frequency changes.

When you add weight to your car, the natural frequency of your car changes and the car will experience increased vibrations at different speeds.

timmbo

IMO, I guess what matters to me is at what speeds and driving style I'm at 95% of the time. For me that is speeds less than 80mph. IMO anything above 90 your going to run into things like high resonant noise from the exhaust, vibrations whether it be from the driveline or tires/balance etc. I guess what I'm saying is that for my driving style this shaft is perfect. No problems. But it begs the question.........why is the factory shaft a two piece shaft??? There is a reason. Is it because of the wheelbase combined with the set height of the transmission and differential requires it to provide a vibration free environment at all speeds? Think of a single axle straight box truck like a Ryder or something. Those have two piece shafts and for good reason. Like I said, just gets me thinking, why would Ford install a two piece shaft when obviously a one piece would be cheaper? I'm thinking it's the reason I listed above. However I sure would like to know.

shaftmasters

In the case of a Ryder box truck and the like, multiple driveshafts are used because of the lengths involved. I agree that Ford wouldn't be adding costs to these cars with the expensive two-piece design if they didn't feel the need. These cars have design issues that create harmonic vibrations. The OEM driveshafts have a rubber sound deadener inside to mask these harmonics. The OEM panhard bar has a lead shot inside for the same reason. It is fairly uncommon that our customers have issues with one of our driveshafts which is why we offer our unconditional money back guarantee. I think that with some angle adjustment Andrew can increase the point at which the harmonics come in but he is welcome to return it if he decides he isn't happy with it for a full refund.

shaftmasters

Just wanted to let everyone know that since we re-introduced our 3.5" diameter shafts they have become quite popular. We have even shipped shafts to several European countries.

Then we introduced our 3.5" V8 GT Direct Bolt In and it seems to be what people have been waiting for. Thanks to all the Mustang owners who have made this shaft our most popular driveshaft in recent memory.

We would like it to be known that out of all the 3.5" diameter shafts that we have sold, we have heard of only 1 problem (that being Andrew who is keeping people updated on the progress he is making towards vibration elimination).

Dineau

That's great how low does it take for any new orders on V6 3.5" ?

NavAv

Its a great shaft at a MUCH better price than the other brands are charging, so it only makes sense. Keep up the good work guys...

East87

Interesting...and obviously that thought occurred to me as well. Of course a 1-piece is going to completely change the characteristics of the driveline when you talk about things like noise, slop, efficiency, and balance. Some of those characteristics will change for the better, others for the worse. I think we're driving at the same point here. I truly cannot believe that any car can be 100% stock-smooth up to and beyond 135 mph with any one-piece driveshaft. People who say otherwise, it would be interesting to see a video of driving up to those speeds with your aftermarket driveshaft.

At no point in this am I criticizing or even downplaying whatsoever the care that Shaftmasters puts into its product. I am simply saying that perhaps my expectations were a bit high, and I'd like to hear people come out and say "yes well there are certain levels of tolerable harmonic/resonant vibration and an increase in noise that result from installing a one-piece driveshaft" rather than seeing (too often) "smooth as butter up to 140 mph"...I have a hard time believing that I am the only person who has experienced this

Timmbo, I'm curious as to your experience with the driveshaft above your stated sweet spot of 80 mph. I would say EXACTLY what you said about the driveshaft being perfect for sub-80mph driving. It's odd you say that too because I thought the exact same thing driving tonight.

After another drive, it's just fantastic under 80 mph. Above 80, there is increased sound and tactile resonance that borders on vibration. There are twinges of heavy vibrations that are felt around 105-110.

Jer5757

Im gonna b purchasing a DS from shaftmaster in the next week or two and i have bin reading every thread i can find about them and have heard nothing but good things until East187. But i am still gonna purchase one because after all no company is perfect but shaftmaster seems like the best. And there customer service seems to be a plus. Hope you get it figured out East187

Riptide

Hey FWIW I tested the Steeda out today. Got up to just over 110. It's been a long time since I had the car up that fast with the stock driveshaft but as far as I could tell it seems fine. There might be a tiny new vibration that I can barely feel through the seat of my pants but nothing through the steering or the pedal. Certainly nothing obviously wrong where I'm unhappy. And I'm pretty picky.

Not many cars are going to be quiet as a church mouse or 100% smooth at speeds over about 80. Most roads aren't 100% smooth, far from it, and at those speeds IMO some vibration and noise is natural.