Sound in Rear end?

[bbowes9]

Hi everyone, I'm getting a very faint sound in the rear that makes itself more audible at around 50mph-55mph. It sounds like it could be a bearing of some sort but just wanted to get some input. I'll attach the original video with enhanced audio to hear the noise better. Any ideas to what it could be is appreciated.

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[Eyesac]

Have you checked wheel bearings already?

 

[Cobra Jet]

If the noise or vibe decreases when you let off the gas it's possibly a problem with the driven shaft or rear diff. The same is true if you have a manual trans and while driving you put it in neutral, if the noise/vibe sort of subsides it's related to the driveshaft or rear diff. Another test or finding is if the noise/vibe comes on at a certain speed/rpm and gets louder or again the noise/vibe subsides at a certain speed/rpm then it's related to the driveshaft or rear diff.

If the noise is a constant but more present when you lean into a left or right turn or curve usually that is indicative of wheel hub bearing going bad. It will feel like you're driving on gravel as it gets worse. The noise will also not increase or decrease with speed/rpm, it will remain constant.

Jack the car up and do this:

- 1st make sure the axle nuts are torqued secure - they're known to come loose. There's a big thread on here about it. Tighten if loose. Torque all lug nuts to spec.

- 2nd after checking the axle nuts, grasp the wheel at your 12 and 6, then 3 and 9 at each position, give it a firm forward/back and side to side tug at those positions. If there is any play or wobble, it's the rear hub bearings.

- 3rd check the driveshaft center support bearing, the front trans flange and the rear pinion flange for any loose or missing bolts. This has been an issue on some S550's where the bolts are loose and in some instances, they fell out.

If you have choked all of the above and the noise increases/decreases with speed/rpm or does the same when you remove the load from the drivetrain (let off gas or put trans in neutral), it's def drivetrain related as noted in the beginning.

 

[bbowes9]

If the noise or vibe decreases when you let off the gas it's possibly a problem with the driven shaft or rear diff. The same is true if you have a manual trans and while driving you put it in neutral, if the noise/vibe sort of subsides it's related to the driveshaft or rear diff. Another test or finding is if the noise/vibe comes on at a certain speed/rpm and gets louder or again the noise/vibe subsides at a certain speed/rpm then it's related to the driveshaft or rear diff.

If the noise is a constant but more present when you lean into a left or right turn or curve usually that is indicative of wheel hub bearing going bad. It will feel like you're driving on gravel as it gets worse. The noise will also not increase or decrease with speed/rpm, it will remain constant.

Jack the car up and do this:

- 1st make sure the axle nuts are torqued secure - they're known to come loose. There's a big thread on here about it. Tighten if loose. Torque all lug nuts to spec.

- 2nd after checking the axle nuts, grasp the wheel at your 12 and 6, then 3 and 9 at each position, give it a firm forward/back and side to side tug at those positions. If there is any play or wobble, it's the rear hub bearings.

- 3rd check the driveshaft center support bearing, the front trans flange and the rear pinion flange for any loose or missing bolts. This has been an issue on some S550's where the bolts are loose and in some instances, they fell out.

If you have choked all of the above and the noise increases/decreases with speed/rpm or does the same when you remove the load from the drivetrain (let off gas or put trans in neutral), it's def drivetrain related as noted in the beginning.

Have you checked wheel bearings already?

Thanks for the input, the noise only gets slightly faster as speed goes up, and is more audible when gas is given. turning does not affect the noise at all as well. ill take a look at everything mentioned and report back!

 

[Crew4991]

Have you checked wheel bearings already?

Thanks for the input, the noise only gets slightly faster as speed goes up, and is more audible when gas is given. turning does not affect the noise at all as well. ill take a look at everything mentioned and report back!

Yes, 100% what @Eyesac said.
Op get those wheel bearings checked and replaced. When they start to go they make that howling sound. The only howling sound we want around here is that coyote in the engine bay.

 

[bbowes9]

Finally got around to checking things out. i checked for any loose parts and nothing seemed off. Put the car on jacks in the rear and was able to hear the same sound towards the rear end when it was at about 20-25mph. Ended up taking off both rear wheels and checking the hub bearings but they seemed smooth. I'm thinking it could possibly be the differential.

 

[Pistol_91]

Sounds like wheel bearings. Do you beat the hell out of your car for it to be the diff? Like cobra jet said does it get better/worse with throttle input? No? Then its probably a wheel bearing thats what typically makes that roaring sound on most cars. Wheel bearings are cheap and easy to change. Id start there.

 

[bbowes9]

Sounds like wheel bearings. Do you beat the hell out of your car for it to be the diff? Like cobra jet said does it get better/worse with throttle input? No? Then its probably a wheel bearing thats what typically makes that roaring sound on most cars. Wheel bearings are cheap and easy to change. Id start there.

Yes it does get slightly louder when giving more throttle. I don't beat on the car so that's why its just really weird for that to be the issue. I'm taking it to a shop to be properly diagnosed tomorrow since I really don't have experience in diagnosing bad bearings on any car. I'll reply if they can figure it out!

 

[bbowes9]

Shop confirmed the differential is bad. Thanks for the help and pointing me in the right direction.

 

[shadowx]

Shop confirmed the differential is bad. Thanks for the help and pointing me in the right direction.

What was wrong with it? And did you just replace the whole diff?

 

[bbowes9]

What was wrong with it? And did you just replace the whole diff?

I wish I knew specifically what was wrong with the diff but I don't. Shops around me were quoting more to fix the faulty diff than to just replace it entirely. I ended up replacing the entire diff and its been perfect since (about 17,000 miles later), no sound.

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