Humming sound..can't figure it out..audio attached

mal81394 · Post by **mal81394** » 10 Mar 2018, 19:27

Haven't had a chance to check the mounts yet as the weather has been bad...however I haven noticed something. When I swerve to the right the sound goes away briefly and then returns when I drive straight again. When I swerve to the left the sound gets worse. Does this attribute to anything?

Post by **SuperHerman** » 17 Mar 2018, 19:09

Here is an update. I sent the car off with my mechanic to have several things tended to. My shoulder is still recovering from a ski injury and at $50/hr I will pay that any day. That said, the shop checked the wheel bearings and they were fine. They put the car on the hoist, ran it and isolated the noise to the front propeller shaft CV joint. So I ordered the part and hopefully will have the noise solved - if it is not said CV joint - it could be a bearing in the front diff.

A few months ago I had another mechanic relube the front and rear CV as I chased the noise - but it appears the propeller shaft front CV may have already have been bad. That is why I eliminated it from the list. First mechanic did say that the lube in there was hard and crusty. Common issue. Once the new part is installed I will update.

mal81394 · Post by **mal81394** » 19 Mar 2018, 14:43

Great! Can't wait to hear if that is it!!

mal81394 · Post by **mal81394** » 27 Mar 2018, 20:37

SuperHerman wrote: ↑17 Mar 2018, 19:09 Here is an update. I sent the car off with my mechanic to have several things tended to. My shoulder is still recovering from a ski injury and at $50/hr I will pay that any day. That said, the shop checked the wheel bearings and they were fine. They put the car on the hoist, ran it and isolated the noise to the front propeller shaft CV joint. So I ordered the part and hopefully will have the noise solved - if it is not said CV joint - it could be a bearing in the front diff.

A few months ago I had another mechanic relube the front and rear CV as I chased the noise - but it appears the propeller shaft front CV may have already have been bad. That is why I eliminated it from the list. First mechanic did say that the lube in there was hard and crusty. Common issue. Once the new part is installed I will update.

Hey SuperHerman any updates on this?? Thanks

Post by **SuperHerman** » 28 Mar 2018, 10:43

Update - I had the front prop shaft CV replaced yesterday. Noise has moved from 50-60 range to 68mph plus. The front CV prop shaft has improved things - installer said the boot was torn and there was not sufficient grease in the joint. When they did the diagnosis they listened to everything under the car while it was on the lift and under power. The noise was coming from the CV prop shaft joint after repair it was gone. I am going in today to get a new set of tires with the hope it solves the problem. If not we are looking at the wheel bearings which appear fine under inspection. I will update.

mal81394 · Post by **mal81394** » 28 Mar 2018, 14:48

Great thanks for keeping me in the loop. Mine is most prevalent in that 68mph range as well but then dies at 70. I am beginning to think tires as well...and if so I will keep driving as is. Look forward to what new tires does for you.

Post by **SuperHerman** » 28 Mar 2018, 16:19

Well I am $700 poorer and sound is still there. Tires did not fix the issue. Next will be the wheel bearings and maybe the left CV axle as I have a spare.

OldMD2B · Post by **OldMD2B** » 29 Mar 2018, 19:58

It is difficult to determine just what I am hearing in the audio/video, but it sounds like the droning (loud, then softer, then louder again) of a beat frequency. Happens when at least two frequencies are very similar to each other, but not exactly the same. The beat frequency is the difference between the two "parent" frequencies (F1-F2 = Beat freq., i.e. 100 Hz - 90 Hz = 10 Hz).

If that is what I'm hearing, you'd be looking for the sources of the "parent" frequencies.

If that's not what I'm hearing..., well, then nevermind...

Good luck. I'm in need of a prop shaft replacement as well. I get a prominent noise and vibration from 36-40 mph, and then less significant vibration at about double that range. I was told the prop shaft is out of balance and that the carrier bearing has too much play. Not keen on the $700 to replace the shaft, so I might just remove it and run FWD now that winter is basically over up here in the snow belt of NE Ohio. Also need to replace the lower motor mounts, so that may be contributing to the vibration as well.

mal81394 · Post by **mal81394** » 02 Apr 2018, 21:47

OldMD2B wrote: ↑29 Mar 2018, 19:58 It is difficult to determine just what I am hearing in the audio/video, but it sounds like the droning (loud, then softer, then louder again) of a beat frequency. Happens when at least two frequencies are very similar to each other, but not exactly the same. The beat frequency is the difference between the two "parent" frequencies (F1-F2 = Beat freq., i.e. 100 Hz - 90 Hz = 10 Hz).

If that is what I'm hearing, you'd be looking for the sources of the "parent" frequencies.

If that's not what I'm hearing..., well, then nevermind...

Good luck. I'm in need of a prop shaft replacement as well. I get a prominent noise and vibration from 36-40 mph, and then less significant vibration at about double that range. I was told the prop shaft is out of balance and that the carrier bearing has too much play. Not keen on the $700 to replace the shaft, so I might just remove it and run FWD now that winter is basically over up here in the snow belt of NE Ohio. Also need to replace the lower motor mounts, so that may be contributing to the vibration as well.

Yes...you are exactly right it is the droning noise of different frequencies. I still need to check my motor mounts to see if maybe this is harmonic resonance. From your point of view OLDMD2B, any idea what these parent frequencies may be?

Post by **SuperHerman** » 07 Apr 2018, 21:09

Latest update. My guys pulled the wheel bearings and they were 144k old but felt good. They will be replaced regardless as I bought new ones. I will swap out the left CV as I have a spare with only 75k on it, just to eliminate one other item.

In the process they found metal in the chain drive front differential. Original thought was the final gear was the issue, but when they ripped into that they found it all intact and looking fine. Thought now is the metal was from a seal spring that became dislodged and was chomped up. Parts are on order and will have the front differential resealed and examined. Tranny pan showed now signs of metal out of the norm, just tiny amounts on the magnets and the fluid looked great as it only has 10k max on it.

So once that is done I will report back on whether the new used CV and wheel bearings solve the problem.

Humming sound..can't figure it out..audio attached

Re: Humming sound..can't figure it out..audio attached