2015 GT Manual Buzzing Noise

[S550_Matt]

Hi all,

In march I decided to replace the DS with Dynotech's one piece aluminum DS. The car has been running great until I got this buzzing and loud vibrating sound.

Let me explain, When I turn the car on from a cold start is when I started to notice it the most. But it went away after the car reached normal operating temp. but now it happens constantly . Every time I shift around 2200-2800 I hear a short buzz sound coming from the transmission/front DS area. I also noticed after 10 minutes of driving, when I put the car in neutral to coast I hear a very loud vibrating sound. These two things started at the same time.

I did some poking around online and found the old TSB from 05-08 Mustangs:

TSB 08-2-10

"Some 2005-2008 Mustang vehicles built before 12/13/2007 and equipped with a 4.6L engine and manual transmission, may exhibit an oil-canning or exhaust rattle/buzz around 2000 - 2500 RPM during the first few minutes of driving after a cold start. The sound goes away after the car warms up."

Im going to take my car to the dealer tomorrow, but has anyone else had this come up?

4.8k Miles.

Thanks!
Matt

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[S550_Matt]

So I took the car to the dealer yesterday. The mechanic is saying its the DS, though his explanation wasn't clear. He said the DS was bad and that all 1-Piece DS are bad, saying that the reason for the 2 piece was to give a better pinion angle and thats why ford designed it that way. From my understanding, IRSs dont need to have the pinion flange angled?

I mentioned that I have seen where 2 piece DSs are heavier and weaker because of the joint in the middle that can cause flex and snap under high load. But he disregarded my statement and said it doesn't make a difference, you wont feel the car going faster nor is it lighter. I got kind of frustrated, so I tried one last time to tell him the specs of it, being lighter and its rated up to 900HP. But he kept insisting the DS is bad.

He said he's going to put the stock on back on and see if the sound goes away. I feel like it will because the rubber will absorb any sounds it would have made. Lets see how is goes I guess.

 

[FordTechOne]

So I took the car to the dealer yesterday. The mechanic is saying its the DS, though his explanation wasn't clear. He said the DS was bad and that all 1-Piece DS are bad, saying that the reason for the 2 piece was to give a better pinion angle and thats why ford designed it that way. From my understanding, IRSs dont need to have the pinion flange angled?

I mentioned that I have seen where 2 piece DSs are heavier and weaker because of the joint in the middle that can cause flex and snap under high load. But he disregarded my statement and said it doesn't make a difference, you wont feel the car going faster nor is it lighter. I got kind of frustrated, so I tried one last time to tell him the specs of it, being lighter and its rated up to 900HP. But he kept insisting the DS is bad.

He said he's going to put the stock on back on and see if the sound goes away. I feel like it will because the rubber will absorb any sounds it would have made. Lets see how is goes I guess.

Although the issue may not be the aluminum driveshaft itself, it is incorrect that pinion angle does not matter with IRS. Pinion angle is critical regardless of suspension design, as the U-joints must be in phase with each other. The benefit of IRS is that the pinion angle does not change with suspension movement, aside from the deflection that occurs under acceleration/deceleration. Aftermarket high durometer differential bushings can minimize that deflection, but at the cost of a potential increase in NVH (Noise, Vibration, Harshness).

Arguing with the dealer will not get you very far, and the simple truth is because they are trained to diagnose issues with factory systems and components. They are not engineers, so they cannot determine the affects that aftermarket parts and modifications will have on the vehicle. They are paid to repair vehicle defects under warranty, and the only way they can do that is to diagnose the vehicle based on the published information with the vehicle in it's factory condition. Your aftermarket driveshaft throws a wrench into that equation, which is why the dealer suggested swapping the driveshaft back to factory for diagnosis.

A 1 piece aluminum driveshaft certainly isn't bad, and can offer a nice upgrade from the steel 2 piece unit. However, without calculating driveline angles, there is no way to know if it's inducing your vibration concern. You may want to contact DynoTech directly to see what they say, they may have some helpful information regarding the concern you are having.

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