LOUD HOWL/WHINE AFTER SUBFRAME WORK

[GuardedGT]

Hey guys,

over the weekend I installed the CB010 kit, BMR alignment sleeves, and differential poly inserts to try and tighten up my driveline and eliminate some wheel hop.

Install was a success, but on the test drive I noticed a howl/whine coming from the rear. It sounds like it’s coming from the left side but not totally sure.

I checked the tire, at first thinking something was rubbing but nothing. I checked the movement in the wheel and it was solid.

These kits do say that there can be a slight increase in NVH, but this is no slight increase.

It sounds like the noise is differential related, I reciently did a gear oil change and there was nothing out of the ordinary on the plug, just some metallic sludge with no major chunks. Fluid was topped up with royal purple and filled till it started to seep out from the fill plug.

After watching some videos I stumbled across a bad pinion bearing and it seems to be a similar noise, though it was a different vehicle.

For my case, it’s the worst at 50mph when cruising, and goes away if I give it some throttle. I’m going to check the amount of play in the pinion by rotating the drive shaft and go from there.

IF IT IS THE PINION BEARING, can I just change the bearing, seal, and crush sleeve? Or do I need to do a total rebuild?

Still uncertain whether or not this is the source of my noise, but looking for suggestions to determine exactly what it could be and what is necessary to fix it. I have basic hand tools and a jack/jack stands.

Any suggestions or thoughts are appreciated! Thanks.

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[ray=out]

Which poly inserts did you use? These cars are pretty NVH sensitive with driveline changes and everyone's NVH tolerance is different.

 

[GuardedGT]

I put in the BMR red poly bushing inserts. I don’t have much experience with NVH, but it’s loud loud. Especially at cruise.

 

[sk47]

I reciently did a gear oil change and there was nothing out of the ordinary on the plug, just some metallic sludge with no major chunks.

Hello; If you put on some miles after the gear oil change and before the new bushings there is little reason to suspect the rear end parts. Not out of the question of course.

There is a reason companies isolate suspension and running gear with rubber or other such stuff. The harder poly bushing inserts should tighten up (remove play) but it is my take transfer more noise. May be a natural outcome of the product.

 

[GuardedGT]

I’ve been doing some digging and it really sounds like it could be the pinion bearing. I’ve got the 3.73 Torsen and the crunch sleeve has been known to loosen over time. Is it possible the increase in noise just uncovered something that was already there??

 

[Oakley]

I put in the BMR red poly bushing inserts. I don’t have much experience with NVH, but it’s loud loud. Especially at cruise.

its that way because you did the front poly inserts where the pinion gear rides. I did the big bertha bolts and kelltrac inserts but only in the rear and had no noticeable increase in nvh. that was like 6K miles ago and the car is awesome.

morons at the time told me I was half-assing it but every time i see posts like this it confirms how stupid they are. revert the front 2 diff bushings back to stock and you'll be fine.

 

[lo-fi]

You could be correct, but polys, solids, and differentials don't mix where noise is concerned. Gear whine is real. Personally I hate poly, less benefits than solid, but with close to all the noise.

On one of my other cars I went solid subframe bushings, solid RTABs, but kept the diff bushings stock rubber. On that particular car I had installed poly in the subframe first, two weeks later I dropped the rear again to install the solid.

 

[sk47]

I’ve been doing some digging and it really sounds like it could be the pinion bearing. I’ve got the 3.73 Torsen and the crunch sleeve has been known to loosen over time. Is it possible the increase in noise just uncovered something that was already there??

Hello; You posted the gear oil was recently changed with no concerning metal bits showing up. I am guessing you did not mess with the pinion nut. Then put in hard bushings and now hear noise.

I suppose you could check the torque of the pinion assembly the way it is done when assembling a rear end. That would entail removing the cover and draining the gear oil and removing the big gear. Maybe just remove the cover and check the gears.

Some have suggested moving the bushings based on experience. Just depends on how much this bothers you.

Many years ago, my brother became convinced the wheel bearings were going bad in the rear end of his F-150. I hauled some tools to his place, and we pulled the axels. I looked at the bearings and the surfaces and did not see anything wrong. He insisted on changing them which involved using a slide hammer to get the bearings out. An involved effort. Then we installed new bearings + seals + new gear oil. Did not fix the issue.
Turned out to be the lug nuts. He had had some nice aftermarket wheels on the truck but sold them and put the stock wheels back on. He liked the nicer lug nuts of the aftermarket wheels so used them rather than the stock type with open ends. The fancy lug nuts were not open and tightened against the end of the lug stud and not the stock wheels. Left just enough play to rumble.

 

[Midlife Mustang]

I have the same bushings on my ‘22 GT with only 4k miles and it whines the exact same way. It’s most likely the bushings.

 

[GuardedGT]

UPDATE: Ive inspected the drive shaft and saw that there was about 1mm of axial play between the drive shaft and the pinion. So I guess this points to a loss in preload? I changed the gear oil, inspected it with a flashlight and saw very minimal metallic sludge built up on the metal, barely noticeable. I’m taking it to a shop tomorrow and discussing having them set the preload.

If this is the case, is it worth upgrading to an aftermarket shim for preload? The factory crush sleeve sounds like a problem for people once they start to do hard launches and I want to ensure that I don’t have to do this again.

Thanks everyone, I’ll keep you all updated!

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