"Drone" on the highway

S

SteveG66

Member
I am a new subscriber, so please be kind(flame2)

I have searched the net and found 0 help, so, hopefully you all may be able to help me out.

We have an 07 GT AWD CX9. It's my wifes car and sadly I get to drive it when it needs gas, service, or a wash.

We took it to my inlaws over Thanksgiving and I noticed that around 57 mph we get a drone or hum on the road. I figured it was caused by the road.

We again took it this past weekend on a trip and noticed the same drone. It begins around 50, hits its peak at 57 and drops out at around 60. It comes back around 75 mph.

I can get that noice to instantly disappear by dropping it into neutral and I can get it to reappear by putting it into drive.

Any idea what may be causing this? I could take it to the dealer, but, figured I'd check with all of the current owners and perhaps experts.

Thanks again,
SteveG
 
Could be the cross-bars on the roof...

Do you happen to have the cross-bars on the roof rails?
If yes, move them all the way to the back.
Also, check if they were installed correctly (front/back sides).
Cross-bars are known to cause low-freq sound at high speed due to aerodynamic disturbance. If you install a wind-deflector for the sunroof (if you had one), it would also reduce the impact. Just guessing here.
 
could be a wheel bearing, I thought i saw a technical service bulletin on that, putting the car in neutral will take the load off of a bearing reducing the whine or least changing the sound.

good luck,
 
Sorry I havent been back to the forums, like I said, It's my wifes car and I only drive it when it needs something.

We took it on a trip again and the noise is still there. At exactly 56-7 mph the noise is its worst.

I scheduled an appointment with Mazda for 2 recalls and asked to have a couple other issues looked at: Rust on the tailgate and the humming noise.

The dealer was great, they gave me a rental (free) to use while they had my car and performed the service as requested.

The recalls were completed, noted the rust on the tailgate and will fix and tried to diagnose the noise.

At first they said they couldnt find the noise, I was quite specific, and then they were able to hear the noise. The service writer said they thought it might be a bearing and they would have to look at it on the following day (today). I got a call and was told they looked at fluids, oils, driveline, and bearings and all appeared normal. They noted that the tires have slight feathering on the inside shoulder and that I need a wheel alignment. Original Duelers have 24k on them.

I cant locate exactly where the noise is coming from, so unfortunatley, I must rely on the dealer to tell me that the noise followed the tire from rear to the right front. Again, all I hear is the noise, just not sure where it's coming from.

Does this all sound right?

How do I know if it isnt the tires and is indeed the bearings or something else?

Thanks again and I promise to check again sooner.

Steve
 
I;d also guess tires. Even a couple of rocks lodged in the tread at the right spot and spacing can create the proper harmonics to cause the 'drone'. Otherwise, uneven wear also can.

Bearings can also, but typically cause a higher pitched whine or squeal.
 
Thanks for the replies, I hope the noise goes away with new shoes......

I've been looking a bit and think we'll end up with the Yokos, seem to have the better reviews and price isnt as bad as the Michelins. I think Discount tire has them for 175 each.

We leased this vehicle for 3 years and 45k, this should be the only set of tires we have to buy for it. I'd really be PO'd if we had leased for 2 years and 30k miles. We'd basically be turning it in with fairly new tires which was my concern with the 3 year and 45,000 miles.

When we get the new tires, i'll send out a quick post to let you all know if the noise went away.

Thanks again for your interest.

Happy Easter,
Steve
 
Not sure if the CX9 uses the same AWD system as the Mazdaspeed 6 but on my old Speed, the diff would drone at 45 MPH like clock work. On the Speed, you could slightly pull up the E-Brake (circuit would disengage the rear wheels) and it would go away. Known issue, no fix.
 
How could it be the tires when putting it to Drive vs. Neutral makes a difference? I am guessing the power-train.
 
Whatever it is, shifting to neutral changes the speed, and the pressure on the driveline. A harmonic whine will be disrupted with very small changes.

Could be the rear drive shaft slightly out of balance too. I'd have to hear it to know for sure.
 
ceric said:
How could it be the tires when putting it to Drive vs. Neutral makes a difference? I am guessing the power-train.
Click to expand...

my mechanical knowledge is limited, but I have to agree with this logic. tires could cause a drone, but that doesn't sound to be the case here... although that depends on the specifics of the test. if he hits 57 and throws it in neutral and the drone immediately goes away, it's not tires... it will take a few seconds before dropping below the low-end threshold of 50. On the other hand, if he puts it in neutral at 50, we can't rule out tires.

Steve, maybe you can confirm how you're doing that test.
 
You'd be surprised how little it takes to disrupt harmonics, especially on a flexible surface like a tire. The force of the engine driving the tires changes the shape of the tread slightly.

Without hearing it though, none of us can know for sure what the noise is. Take it in.
 
I want to apolgise, it's been a couple weeks.

We still havent gotten the new tires, I just hate spending 800+ for new tires although I've always suspected that we would.

I havent gotten to play around with the CX lately, so I cant be absolutely sure the sound goes away based on putting it into neutral while doing 57 mph or not. Once I get a chance to get it on a longer stretch of road, i'll play around.

Thanks again,
Steve
 
I have a 08 cx 9 AWD, and have experienced a sound as well that may be like your droning. It occurs always in 6th gear, and very noticable going up slight to moderate inclines at about 50 mph.

when i manually shift it into 5th gear, the droning stops...back into 6th gear the droning reappears.

Took a brand new 2009 CX 9 FWD out with the service manager. It had the same noise and at the same speed/incline...just to a slightly lesser extend but same pitch and everything. It also disappeared when shifted into 5th.
 
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Hmmm,
The only differences between 5th and 6th gears is rpms (dropped from 5th to 6th) and every things associated with RPMs (which could be the entire powertrain). So, we can rule out speed issue (i.e. not bearings).

You might want to pay attention if the noise is tied to RPM or gears.
Clarifying that can better diagnose the issue.
If gears, your tranny could be at fault here (hope not).
If RPM, it could be some resonance-related issues (even as simple as loose bolts).
 
ceric said:
Hmmm,
The only differences between 5th and 6th gears is rpms (dropped from 5th to 6th) and every things associated with RPMs (which could be the entire powertrain). So, we can rule out speed issue (i.e. not bearings).
Click to expand...

Forgive me if I'm wrong, but the difference between fifth and sixth gear is an entire overdrive unit, and that could definitely account for the OP's drone.

In any event, I would put my best guess into a driveline issue because a bearing would have the drone at lower speeds and continue to increase as speed increases. It would not magically disappear between 60 to 75 mph.

Stay on the dealer, get Mazda involved. My original selling dealer blamed my mirror vibration on a tire balance issue, total BS, to the point that the second dealer ordered a new morror (that's still on back order, BTW). Dealers are fond of blaming unrelated issues when they have no idea what the root source of the problem is. Maybe your tires are feathered, and maybe you are getting some road noise from them, but I'd bet new tires would not solve your issue. Good luck.
 
badself,
what I meant was that when shifting from 5th to 6th or vice versa, at that moment, the only change is the gearing, which changes RPMs of engine (therefore, entire rotational speed of drivetrains).
I am hoping it is not the transmission, but it could be.
That is why it is the first step to see if the droning is RPM-dependent or gear-dependent.
It makes a lot of difference. i.e. I can also reach the same RPM at 1,2,3rd gear. Does the droning happen, then?
 
Actually (and not to get into a spitting match with anyone) overdrive ratio is exactly 1:1, meaning for each turn of the driveshaft the drive wheels rotate one complete revolution. That being the case, if 5th and 6th are both OD, then why don't they each turn at the exact same rpm (5th obviously turns at higher RPM than 6th). Again, I'm looking to learn rather than argue with people.
 
You need spit to get into a spitting match.

Overdrive is 1:1 +X . The term itself refers to the output shaft turning faster than the input shaft, thus being overdriven. So ANY gearing resulting in 1:1 +X is overdrive.

Modern Aisin transmissions like ours do not have a separate overdrive unit. It is a 6 speed, with the two top gears being overdrive. Our CR-V was a 3 speed auto with a separate overdrive unit thus creating a '4th gear'.

FYI:

First gear.........4.15:1
Second gear is 2.37:1
Third gear is.....1.56:1
Fourth gear is...1.15:1
Fifth gear is......0.86:1
Sixth gear is.....0.69:1

So according to your definition, a CX9 has no overdrive.
 
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