As the title says Im having a problem with my alum. driveshaft vibrating at speeds above 80mph. The shop where I purchased and had the driveshaft installed has been very helpful but the problem still persists. They even replaced the shaft with a new one but the problem remained the same. Im at the point where Im about to give up on the shaft and go back to the factory 2 piece.I know several people who have the same shaft as I do installed by the same shop and they have no problems whatsoever, I probably just have one of those few cars that has a tendency to vibrate. If anyone has any advice as to what can be done to stop the vibration I would greatly appreciate it.

Rob

 

The problem is most likely your pinion angle. try getting a hold of an adjustable upper control arm. cheperformance.com makes a good one, as well as some others.

The Straight Scoop on Pinion Angles


by Ron Rygelski
Performance Products-Red Line Synthetic Oil
http://www.myoilshop.com
(formerly www.redlineoilracing.com)
rlracing@sgi.net


Myth #1: The pinion angle somehow affects how much traction the car
will achieve.

Straight Scoop: No way. The pinion angle doesn't mean squat as far
as the rear suspension is concerned. Think about it: why would the
suspension care about u-joint angles? What determines the "hit" on
the rear tires and the rate and amount of weight transfer is the
intersect point of the upper and lower rear bars (control arms).
That's known as the "instant center" (IC), and combined with weight
distribution, spring rates, and shock valving is what affects
traction.

Myth #2: You increased the pinion angle and the result was increased
traction, so Myth #1 must be correct.

Straight Scoop: You haven't been listening. Pinion angle doesn't
affect traction. What happened is you shortened the length of the
upper bars and that changed the intersect point, moving the IC
farther forward. You also screwed up the pinion angle in the
process. If you want to change the length of the upper or lower
bars, or change their mounting points, that's fine. But after you're
done you've got to go back and check and properly reset the pinion
angle.

Myth #3: The garage floor is the correct reference point for
measuring the pinion angle.

Straight Scoop: You've got to be kidding, right? The garage floor
doesn't have anything to do with anything. What's important is the
drivetrain angle. It so happens that professionally built racecars
are constructed so that the crankshaft is parallel to the floor,
meaning that the transmission output shaft will also be parallel to
the floor. But this usually doesn't hold true for cars using a
factory chassis. In most of those cases the engine is tipped
rearward. Take a look under the hood of your Buick and you'll see
what I mean. The drivetrain angle is the reference point and is
considered to be zero.

How to Measure It: The best way to do this is with the car supported
on jackstands, with stands under the front control arms and rear axle
tubes, with the full weight of the car resting on the stands. Next,
it's best to remove the driveshaft. Using an angle finder (these are
available from Competition Engineering or at Sears Hardware stores--
they're a commonly used carpenters tool), measure across the surface
of the rear transmission seal vertically(see illustration 1). This
surface is perpendicular to the output shaft of the trans, so
subtract the measurement from 90 to get the drivetrain angle. Let's
say that the measurement is -2 degrees(pointed down). That is our
reference point. Look at illustration #3. The pinion angle is the
difference in the angle of the rearend to the angle of the
drivetrain. So, in order to have zero pinion angle, the rearend
would have to be tipped upward (pinion yoke pointing upward) 2
degrees. If our drivetrain angle measured -5 degrees, we'd have to
tip the rearend upward 5 degrees to have zero pinion angle. Get it?
Now turn the pinion yoke so that the u-joint cups are sideways, and
measure across one side of the pinion yoke vertically(see
illustration 1) where the u-joint strap connects. Again, this
surface is perpendicular to the pinion, so subtract the measurement
from 90 to get the rearend angle. compare this number to the
drivetrain angle to get the pinion angle. If the drivetrain angle
was -2 degrees(pointed down), and the rearend angle measured +1
degrees(pointed up), then the pinion angle would be -1 degree. If
the drivetrain angle had measured -2 degrees (pointed down) and the
rearend angle had measured -3 degrees (pointed down) then the pinion
angle would be -5 degrees. In my particular case, the drivetrain
angle measured -4 degrees, and the rearend angle measured -6 degrees,
resulting in a pinion angle of -10 degrees, a wasted tailshaft
bushing, and a slower than necessary racecar. The idea is to have
the pinion angle at zero with the racecar under power and going down
the track. To allow for suspension movement and loading, the pinion
angle should be at around -2 degrees for our cars.

Illustration 1

http://www.buickperformance.com/pinionangle1.jpg

Illustration 2

http://www.buickperformance.com/pinionangle2.JPG

Illustration 3

http://www.buickperformance.com/pinionangle3.JPG


How to Adjust It: You can purchase adjustable upper or lower control
arms from a variety of sources, or you can weld washers to the
factory control arms and re-drill the pivot holes in a new location,
or you can cut and weld the factory control arms.

How important is all of this: Well, excessive pinion angle can bind
the u-joints up pretty good and rob quite a bit of horsepower. It's
not at all unusual for a car to pick up 2-3 tenths and as many mph
after getting this straightened out. Also, excessive pinion angle is
often the real culprit behind broken parts. Racers love to attribute
busted driveshafts, exploded tailshafts, and cracked bellhousing to
the raw torque and horsepower produced by their motors, when in fact
it's usually a problem with driveline geometry. It's definitely
worth checking before you break something expensive. See you in the
lanes!!

 

Thanks for the info Banned, I will look into an adjustable uca. Do you happen to know the correct angle for our cars?

 

shaftmasters
Premier Authorized Advertiser




Join Date: November 30, 2007
Posts: 173



In response to recent posts elsewhere on this forum we would like to say:
"It sure feels good being vindicated"

It has been our position all along that a properly manufactured and balanced single piece aluminum driveshaft will not vibrate. It has also been our contention that there is no need to adjust pinion angles by installing adjustable control arms. Furthermore, it has been our contention that aluminum shafts using adapter plates will not vibrate when installed properly, no matter what transmission you have.

After seeing that a 1 1/2" suspension drop will only change pinion angle by less than 1 degree we feel confident that pinion angle has not been the cause of vibration issues with some aluminum shafts on the market.

After selling over 140 shafts and not having vibration issues with adapter plates we feel confident that "aluminum shafts using adapter plates vibrate with automatic transmissions" is another myth.

After woking closely with blackstang06 and JimC we feel confident that there is absolutely no need to waste time, money and effort installing adjustable control arms. If customers feel compelled to do so, because they want better quality than OEM, we suggest they set them at factory length when installing.
__________________
http://www.shaftmasters.com

 

Thanks for the info. Im realy starting to think that the shaft is alright and its the car. From reading it seems there are a few of us out there that no matter what is tried a 1 piece driveshaft just will not work smoothly on our cars. I have this topic posted on another forum and a memeber over there is having the exact same problem Im having but he has the shaftmasters 3.5" shaft. We have 2 different brands, 2 different diameters, Im not sure if his is using an adapter plate or not but I am. The only things are setup have in common is that its a Mustang. I guess this is the reason Ford used the 2 piece shaft. During testing they probably found that there were a certain percentage of cars that didnt take to the 1 piece shaft.

 

This is Robert from Shaftmasters. I am curious as to which forum and member you are referring to as having problems with one of our shafts. To date there are only two people who have used our 10 day unconditional money back guarantee and returned our driveshaft. Both had done significant suspension modifications which we believe leads to adaptability problems when using aluminum aftermarket driveshafts on these Mustangs. We also believe that a fair amount of misinformation about not only the need to adjust pinion angle but also how to adjust pinion angle and to what setting has contributed to many members vibration problems instead of solving them. It seems as though the angle suggestions started more as a means of trying to solve clearance issues with the 4 inch driveshafts. Going more negative will put the driveshaft futher away from the objects on the tunnel they have been known to rub on and since then whenever anyone mentions vibration problems with aluminum driveshafts the first response is "you need to adjust pinion angle". We have sold over 150 of these shafts with only 2 returns. We feel confident in offering the 10 day unconditional money back guarantee and this hopefully will give members confidence in buying from us knowing that if their not satisfied they can get their money back no questions asked.

 

PM sent.

Rob

 

should be -2 degrees.

 

Rob,
We have followed threads related to aluminum driveshafts posted on the various forums over the last year. We have also sold over 150 of these driveshafts and have received feedback from many of our customers. We like to feel that we can share a better insight into the problems and cures with '05 and up Mustangs relating to the use of aftermarket aluminum driveshafts than individuals who have only their own experience to relate to. Lets assume for the sake of arguement that in any particular vibration problem on a Mustang with an aluminum driveshaft that it is not the quality or manufacturer of the driveshaft that is causing the problem. Here are several of the different factors that in our opinion can cause a vibration problem:
1. incorrect installation of driveshaft, replacement flange or adapter plate.
2. The use of racing type suspension components i.e. adjustable upper and/or lower control arms. saleen watts link etc.
3. Incorrect setting of pinion angle
4. 4:10 gears
5. Aftermarket motor mounts and panhard bars.
In your situation did the shop that installed your driveshaft try to reseat the adapter plate. In our opinion Coast Driveline makes a good product and the first thing to look at should be whether the adapter plate was installed properly. If this was cocked when installed causing it to turn off-centered then the shop could bolt-up 1000 driveshafts to it and everyone would vibrate. This is probably your culprit. If not I would re-examine the install of the 4:10 gears. They tend to cause a gear whine even when installed properly. Fomoco obviously has encountered "harmonic issues" with these Mustangs and has attempted to mask these issues with some of the following:
1. Rubber sound deadener in driveshaft
2. Sound deadener in OEM panhard bar
When Mustang owners in an attempt to improve the performance of their car start to change these components along with changing suspension components using polyurethane bushings instead of rubber bushings in our opinion it shouldn't come as a surprise that harmonic vibrations are going to develop.
In our opinion on 90% of lowered Mustangs the pinion angle does not change enough to warrant adjusting. We would recommend that anyone who wants to use a "racing type rear suspension" not use an aluminum driveshaft, especially if you expect the same noise reduction quality as the OEM driveshaft and suspension.
The few problems that our customers have encountered with our driveshafts have either installed the adapter plate wrong, have "racing type suspension" transmitting harmonics or and have adj. control arms and have their pinion angle off.

 

What does the vibration feel like from a one piece driveshaft that is not balanced correctly, or the one that is on your car stirob? Does the whole car shake??

 

I agree with you 100% Robert ! As you know I am running your 4'' shaft ! and as you also know I installed a adjustable UCA but left the pinion angle at the factory setting. I did take the precaution to relocate the ebrake cable mount and also modify the elongated ridge that was tacobill's point of contact with his rub issue, both of these mods take about 30 minutes total ! I have had my Stang loaded with 4 passengers, 2 in the rear that totaled 300 lb's and have had no contact/rub issues or vibration problems !

 

Thanks for the info. To answer some of your questions yes they tried to reseat the adapter plate, the 4:10 gears are actualy quieter than the 3:55's that came with the car, only suspension mods are Metco lca's. I would also like to point out that the shop that has been doing the work to my car is very knowledgable and specializes in Ford products. I was able to talk to several people with the same shaft I have and they reported zero problems. All of these people had their shaft installed at the same place I did. I can understand where alot of issues with shafts can arise from other factors other than the shaft itself and in this case I believe that to be the problem also and blame my particular car for the vibration. Thankou again for your input as the points you bring up are very valid and could and do cause problems for others. Unfortunetly for me there seems to be no easy answer with the only avenue not ventured is the installation of an adjustable uca with pinion angle being reset. I dont beleive Ill be trying this as I dont want to spend another $300 on somehting that may or may not work.

Rob

 

This caught my eye as it is the first time I heard it. I am in middle of installing the new spydershaft and have 4.10s, but my car is not lowered. The 4.10s were installed by a reputable installer that was highly recommended by many on a local forum. They have been in for at least a year (maybe 3-4k miles) without a noticeable problem.

Should I have a slight concern?

 

The vibration starts as a light buzzing and gradualy increases with speed. In my case the vibration gets so bad the entire car shakes.

Rob

 

I want to be clear on our opinion as it relates to 4:10 gears causing a possible vibration problem when used on a Mustang that also has an aluminum driveshaft. The 4:10 gears are going to cause the driveshaft to spin at higher rpm's then the OEM gear ratio. The higher the maximum rpm's a driveshaft has to spin at increases the possibility of a vibration problem. Depending on the manufacturer of the gear set and who does the installation is a big factor in whether you realize gear whine from the 4:10 gears which could cause a harmonic vibration being transmitted thru an aluminum driveshaft whereas the OEM driveshaft would probably mask it.

 

This post looks really fishy...

 

Interesting comment. I added the 4.10's, Spydershaft and CHE K member with TL all within one week of each other. I picked up NVH at 62-65 mph but went away after that - had it up to 90+ with no vibrations. Took the car out to Ron's garage and he rotated the shaft 180 which helped cut down on the NVH - still there at around 60-62 but not as bad. Wonder if the 4.10's add to the problem - they are FRRP's BTW.

 

Mine are FRRP too. Hopefully I will be able test this later this week when the rain stops.

 

which post?

 

I agree, one thing I am not seeing here is solutions offered for high speed vibration, used to be one would check the tire balance, guess that doesnt matter anymore?