Noise from rear after installing M226

[xyoverland]

M226 install went fine into my 2015 S but I noticed that at about any speed, there’s a low-pitched warbling noise coming from the rear. It’s very hard to explain but sometimes when you put just one rear window down and get that pulsating low frequency - kind of like that.

I’m fairly sure I can’t feel anything, just hear it. Any ideas what this could be?

It also feels like there’s ever so slightly more friction than I used to have like it slows down quicker when letting off the gas than it used to. Not sure if that’s related or not. I did verify my parking brake is adjusted to not be touching.

 

[Muadeeb]

What's the history of the axle? Did you have someone regear it? Was it just a junkyard pull and install?

 

[xyoverland]

What's the history of the axle? Did you have someone regear it? Was it just a junkyard pull and install?

It was out of a running 2008 manual S with 196k. The frame had bad rust and something had eaten the wiring harness, so the guy used it as a donor engine for a better body then parted out the rest.

Axle had some surface rust and the dust shields were rusted to almost nothing, but that’s not strange for the NE.

 

[Prime]

Given the conditions it sounds like a wheel bearing

 

[xyoverland]

Given the conditions it sounds like a wheel bearing

I was hoping the noise not being there at the same speed but coasting would mean it’s not that. I’ll swerve around on the way home to see if it changes when I shift left or right.

 

[xyoverland]

No change doing hard left or right turns. Only above about 20mph and only when accelerating or braking. Coasting the noise goes away.

The audio isn’t great due to wind noise and road debris, but you can kinda hear it I think around the 0:30 mark in this video.

View: https://youtu.be/UmiML8LMfK8?si=avDlTDwd6l4R-gr_


The clicking you hear around 0:40 till the end of the video is my driver side front. Don’t know yet if that’s the bearing or a stuck brake slide pin.

 

[TerryD]

Check pinion play. Set park brake and put the X in neutral. Check for up/down or in/out play.

What did the old fluid look like?

As for letting off and slowing down, that's probably a function of better engine breaking with the lower gears.

 

[xyoverland]

Check pinion play. Set park brake and put the X in neutral. Check for up/down or in/out play.

What did the old fluid look like?

As for letting off and slowing down, that's probably a function of better engine breaking with the lower gears.

Fluid looked good. I’ll check play in the morning.

Also got it up on jack stands and up to 25mph no noise. Definitely just under load.

When I hooked up the front driveshaft to the diff I noted the yellow paint mark on the flange and matched that to the yellow on my driveshaft. It was at that point I realized I didn’t mark the yellow spot on the rear axle before painting it with rust reformer. Could it just be an imbalance there?

 

[TerryD]

No

 

[xyoverland]

Update. I saw a picture of somebody else’s Ballistic Fab cover and it looked like their fill plug was about 3/4” higher than mine. It wasn’t the high fill option – that’s way higher. While I did jack the rear up slightly to fill the first time, this time I put front tires out of the garage and jacked it up till the diff was sitting almost level, and added another ~1/3 a quart or so. The noise is still barely there but significantly quieter. Like instead of hearing it over the radio loud and at all speeds, now only around 30mph and if I have the radio off.