Low frequency drone/vibration at 60ish mph

[LotsaMiles]

Cut to the chase:

I have 163,000 miles on my 2013 FR-S. I've noticed a sound that I originally thought was just road surface related, but can now say that it is drive train related. And it is simple. He're a bulleted list of facts:
1. At around 59-63 mph there is a solid vibration "tone" at around 50 hz (I'm a hi-fi buff. It's lower than a 60 hz AC hum by a little) and then completely disappears as my speed increases.
2. Road surface is irrelevant.
3. It is there regardless of what gear I'm in, and even if I take it out of gear and coast.
4. I don't know if it's getting louder, so I notice it more, or if it's just that as I have listened to it closely over the last few months it is just more apparent to me.

Any thoughts from anyone?

FWIW, I just replaced a rear wheel bearing that was damaged at around 90k miles but had just started making noise. That noise was also a drone, but much higher frequency. And it is not related to this, IMO as this noise was there before the replacement, but was only noticeable to me at around 150k miles.

I thought it might be a driveshaft U-Joint, but then it hit me that the rear differential is fixed in place, so there probably are not U-joints on the drive shaft. And the friquency is way too high for the rear shafts, since they turn a lot slower. Or could it be that IS the problem, and they just have a different bearing at the differential end?

[wparsons]

How old are the tires, any vibrations at the wheel?


There are u-joints in the driveshaft, three of them:

[Lantanafrs2]

U joints will generally start to "clack" but they're a possibility.

[Tcoat]

Originally Posted by Lantanafrs2

U joints will generally start to "clack" but they're a possibility.

Yep. You will usually hear u joints clack or thunk when switch from forward to reverse or vice versa. They generally don't make noise while traveling and if they do it usually get's worse as the speed increases. Never can be 100% sure of how they will act though so can't be automatically ruled out.


Been there a couple of times with other cars.

[Lantanafrs2]

I would start to hear them while driving alongside Jersey barriers

[LotsaMiles]

Thanks for the replies, guys. It sounds like it may not be the U-joints since I've tried to get noise out of it by listening while switching from forward to reverse and back with no sound. I guess that makes it more obscure. Which may be a good or bad thing.


I wonder if it's the tranny. I had the clutch replaced about ten thousand miles ago. The first thing that happened was that they had to change lubes because when cold it was very difficult to get it out of first gear. And now the sychro in most gears is "iffy". To be blunt, If I didn't know this dealership and have a very good relationship with them, I'd suspect they gave me a different transmission. But it makes the same subtle whine (from age) as it did before they fixed the clutch (throw out bearing failure is what necessitated it).

[mrspindlelegs]

It could be the mid-ship bearing that lies near the middle of the driveshaft. They will cause a drone when they get worn out.

[LotsaMiles]

Originally Posted by mrspindlelegs

It could be the mid-ship bearing that lies near the middle of the driveshaft. They will cause a drone when they get worn out.

Now that makes perfect sense. Based on the first picture it looks to be that think inside the support between the two driveshaft parts. It would be just like a wheel bearing, I'm guessing. I'll check it out for play when I get home!

[LotsaMiles]

Originally Posted by mrspindlelegs

It could be the mid-ship bearing that lies near the middle of the driveshaft. They will cause a drone when they get worn out.

And if that IS the issue, it means it's probably not going to be a "must fix now" issue until it makes a pretty bad racket. Well, a lot worse than it is now, anyway.

[Tcoat]

Originally Posted by LotsaMiles

Thanks for the replies, guys. It sounds like it may not be the U-joints since I've tried to get noise out of it by listening while switching from forward to reverse and back with no sound. I guess that makes it more obscure. Which may be a good or bad thing.


I wonder if it's the tranny. I had the clutch replaced about ten thousand miles ago. The first thing that happened was that they had to change lubes because when cold it was very difficult to get it out of first gear. And now the sychro in most gears is "iffy". To be blunt, If I didn't know this dealership and have a very good relationship with them, I'd suspect they gave me a different transmission. But it makes the same subtle whine (from age) as it did before they fixed the clutch (throw out bearing failure is what necessitated it).

@Ultramaroon ?


My tranny has always made a hum but after checking a bunch of test tones on YouTube it is probably more in the 150hz range.

[Tcoat]

Originally Posted by LotsaMiles

And if that IS the issue, it means it's probably not going to be a "must fix now" issue until it makes a pretty bad racket. Well, a lot worse than it is now, anyway.

Unless of course it let's go and comes through the floor.
Been there before as well but with a single piece shaft.

[LotsaMiles]

Originally Posted by Tcoat

@Ultramaroon ?


My tranny has always made a hum but after checking a bunch of test tones on YouTube it is probably more in the 150hz range.

One thing I've learned about putting a lot of miles on the same car on the same roads in a short period of time - you get very familiar with its idiosyncrasies. Little noises that were not there before, handling on a particular corner slightly different than before. And little noises that creep in.


Like this droning noise. I also recently noticed that at around 3k rpm the engine exhaust seems to get a little louder than it used to and then quiet down as it goes up.


One reason I think you may be on to something on this because something like this bearing, with two shafts connecting there, can find a "resonant frequency" where it will get worse, but as speed increases, smooth out. Heck, I could extend it's life by avoiding hanging around 60 mph, assuming this is the problem


My take on this stuff is if you can feel it or hear it, it's causing excessive wear somewhere.

[LotsaMiles]

Originally Posted by Tcoat

Unless of course it let's go and comes through the floor.
Been there before as well but with a single piece shaft.

That could be painful in an FR-S.

[Tcoat]

Originally Posted by LotsaMiles

One thing I've learned about putting a lot of miles on the same car on the same roads in a short period of time - you get very familiar with its idiosyncrasies. Little noises that were not there before, handling on a particular corner slightly different than before. And little noises that creep in.


Like this droning noise. I also recently noticed that at around 3k rpm the engine exhaust seems to get a little louder than it used to and then quiet down as it goes up.


One reason I think you may be on to something on this because something like this bearing, with two shafts connecting there, can find a "resonant frequency" where it will get worse, but as speed increases, smooth out. Heck, I could extend it's life by avoiding hanging around 60 mph, assuming this is the problem


My take on this stuff is if you can feel it or hear it, it's causing excessive wear somewhere.

I hear ya. I am at a bit over 130,000 on my 14 also driven on the same stretch of road so any changes in sound stand right out. Had a stone in a tire last week that made me nervous for a bit.


Could you have an exhaust leak that you are thinking is vibrations?