Strange Noise After 13/14 Driveshaft Upgrade

Hello,

I finally upgraded to the 13/14 CF driveshaft with Tob's adapter. So I take the car for a drive and I hear a strange humming sound coming from the rear end. It only came on at higher RPMs and load didn't seem to effect the noise. I took the car back and lifted it up, I checked the pinion angle and adjusted it so that it is 2 degrees off the trans angel, I checked all the bolts and rotated the driveshaft, nothing looks, sounds or feels wrong. I took the car out again and its still there.

Since I got the driveshaft used from a member here I'm thinking I was sold a bad DS and the CV joint is the culprit, I'm really hoping it isn't that but if it is, how long would a bad CV joint survive? Any other ideas? Could it be just a side effect of a 1 piece driveshaft?

EDIT: For those who did the upgrade, was there an increase in NVH? Can you describe it.

You probably don't want to hear this, but the only options you have is to try another 13-14 driveshaft and see if the noise goes away. You might want to look for driveshaft shops that have a fixture they can run it on. Do you notice any vibration in the car when you hear the hum? Usually a bad joint will show vibration in the rear view mirror.

No vibrations, just the sound. I looked back at the sale thread and the seller said the DS had 5100 miles on it so thats good I guess.
I also lifted the car while the engine running and put it in gear, I went 1-4 gear and nothing abnormal so I guess the car has to be under load.

Unfortunately I don't have access to another 13 DS and we don't have shops that specialize in DS's either .

Have you checked for any clearance issues. All bolts on the adapter are tight and nothing is in a bind? If you have access to a dial indicator, you might check for run out.

You've got a long way to go before you start blaming someone for selling you a bad DS. If you went from the OEM DS to a one piece, you're going to get more NVH. Also, from your description, I can't tell exactly what you did to check/alter the pinion angle.

fullboogie said:

You've got a long way to go before you start blaming someone for selling you a bad DS. If you went from the OEM DS to a one piece, you're going to get more NVH. Also, from your description, I can't tell exactly what you did to check/alter the pinion angle.

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Well first I did not blame anyone, I merely stated my fears about it being used. Second I am looking into this and asking about it hoping it isn't a bad DS.

As for pinion angle, following BMR's video on it, the nose of the diff was lower, about 1.5 degrees on my angle finder. Trans was at the same angle of 1.5 degrees. So I adjusted the angle until the nose of the diff is higher, -1.5 degrees. Note the car was on jack stands.

Catmonkey said:

Have you checked for any clearance issues. All bolts on the adapter are tight and nothing is in a bind? If you have access to a dial indicator, you might check for run out.

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Yes, no clearance issues. Everything is tight and nice and I moved the whole thing bu hind and no bind. I will check for run out and report back.

When you say "I'm thinking I was sold a bad DS" on a public forum - that's blaming someone. Just bad wording I guess.

Did you have the jack stand on the body or the axle I think any adjustment has to be done with the suspension loaded if I’m correct just throwing some things to check

manny231988 said:

Did you have the jack stand on the body or the axle I think any adjustment has to be done with the suspension loaded if I’m correct just throwing some things to check

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I lowered the axle to have access to the UCA, but then verified the angles while the suspension was loaded.
I don't remember seeing or reading that the suspension must be loaded but I'll check again.

Definitely check your driveline angle with the suspension LOADED.

Sample measurement with full poly bushings in rear for clarification:

Transmission output shaft pointing DOWN (-1.5*) minus rear pinion angle pointing UP (+.5*) = -2.0* driveline angle.

“Initial” static driveline angle settings (based on expected deflection of bushing material and suspension under high load):

-3* to -2* full stock rubber bushings

-2* full poly bushings

-1* full spherical bearings/rod ends

Start here and adjust as needed.

^^^ Great explanation.

Just for my own clarification on an acceptable "suspension loaded" technique.

1. Car on the ground, measure from rear wheel/axle center to rear fender edge. Call this measurement "X" inches.
2. Use quickjacks to lift car by frame rail, suspension will be fully unloaded and at full droop.
3. Remove rear springs so rear end is easier to raise up with floor jack.
4. Raise rear end with floor jack so axle center is "X" inches from rear fender edge.
5. Rear suspension is now considered loaded and you can check drive line angle properly.

Is this method considered "suspension loaded" ?

merkyworks said:

...^^^Is this method considered "suspension loaded" ?

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Nope. Car on level surface with weight on all four tires, just as it sits in a garage. You can use Race Ramps or blocks of equal height under each tire to lift the car up, maintaining the same static suspension geometry, so that you can work under the car to take measurements and make adjustments.



*edit - added picture

Just out curiosity, did by chance swap the gear set? Where I am going is don't forget to check the pinion bearing for excessive movement. It could have been masked by the two piece driveshaft. Just something else to check while your under there just in case.. the carbon fiber shaft will absorb some noise but it may be resonating some noise from the axle that the stock DS was hiding.

SCGallo2 said:

Nope. Car on level surface with weight on all four tires, just as it sits in a garage. You can use Race Ramps or blocks of equal height under each tire to lift the car up, maintaining the same static suspension geometry, so that you can work under the car to take measurements and make adjustments.

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Not saying your wrong, just trying to learn.

Why does the front suspension needs to be loaded when the engine and trans are fixed to the chassis? Shops that have two post lifts that lift from chassis points, how would they load the suspension? I've seen them put a pole jack under the k-member (to stop the car from tipping) and then use one or two pole jacks under the rear end to load the suspension. Is this not considered loading the rear suspension?

merkyworks said:

^^^...Is this not considered loading the rear suspension?

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There is more than one way to skin this cat. The method I depicted is the simplest and will produce the best results. A level “drive-on” lift would work just as well. What is important is to duplicate the suspension and driveline angle conditions as if you are driving on the street, because that is where you will feel vibrations or hear noises if measurements and settings are off [and occupant weight and fuel level (weight distribution) can have an effect which necessitates fine tuning].

Yes, you are correct, you can lift all the tires off the ground and then load only the rear suspension with pole jacks. But… how do you know when you have 100% static load on the rear axle or start to redistribute weight front to rear? While it might be good enough for our purposes of dialing in a drive shaft on a street car, I don’t believe it is as accurate as the vehicle’s normal static weight in a level condition. Your vehicle’s suspension rake comes into play with weight distribution also. Part of my occupation involves weighing aircraft, small and large, and determining CG (center of gravity), so pardon me if I take weight distribution a little too seriously.

Your initial inquiry about loading the rear suspension involved removing the rear springs, and after reading it again, I have a better understanding of what you are describing and agree that your initial measurement would be valid, but once you start adjusting the UCA or LCAs or both, you may be introducing other variables (like altering wheelbase which affects weight distribution) depending on how much adjustment is required. I would not do it that way.

Thanks for the insight, you make fair points. Cheers!

So I checked the angle again and adjusted it a bit while the suspension is loaded. It was not off by that much but just in case. I also checked for runout at six different places and the biggest was 0.006" at the adapter.

I took the car out again and the same. I've been driving the car more and focusing on what the sound is, and honestly I'm not sure how to describe it. It closer to engine sound rather than a pure howling. Which was my very impression when I first heard it.

Anyway, I'm taking the car to a shop and maybe they'll see something I don't. If anything I want to know whats normal and whats not.

Alright, I just got the car back from the shop and they concluded nothing wrong with the car or the driveshaft. At this point, I'm taking this howling sound as an increase in NVH because of the upgrade despite reviews saying otherwise.