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E36 M3 (1992-1999) {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999


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Old Wed, Apr-18-2012, 09:50:19 PM   #1
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Default Found the culprit for differential failure (picture in here)



So my front differential bolt snapped which caused my rear differential to thump. My differential mounts are like in brand new condition. It barely have over 3k miles since the install.

Even my bolt was 10.9 upgrade, it will snap! PLEASE INSPECT every time you are under the car!!!!

I have to buy a front differential bolt and differential fluid (redline 75w140). Also I recently acquired 235/40/18 bridgestone rear tires.

EDIT- front mount was bad/half assed pressed.
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Old Wed, Apr-18-2012, 09:54:08 PM   #2
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Default Re: Found the culprit for differential failure (picture in here)

They generally break due to the bushing being bad and allowing excess movement of the diff under load. Might want to change that out as well.
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Old Wed, Apr-18-2012, 09:58:09 PM   #3
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Default Re: Found the culprit for differential failure (picture in here)

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They generally break due to the bushing being bad and allowing excess movement of the diff under load. Might want to change that out as well.
I am pretty sure it broke under load once the supercharger were installed and in addition of lightweight flywheel did hurt it. I am running about 16lbs flywheel so its hard to drive smooth and not letting the rpm drop too low.
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Old Wed, Apr-18-2012, 10:12:38 PM   #4
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Default Re: Found the culprit for differential failure (picture in here)

Others have run high HP and not snapped the grade 10.9 bolt. Just saying, I would check it prior to popping another bolt in there or you may be doing it all again.
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Old Wed, Apr-18-2012, 11:53:03 PM   #5
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Default Re: Found the culprit for differential failure (picture in here)

Not the best pictures but this will work. You be the judge to the condition of mounts. Let me know If i miss something.









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Old Wed, Apr-18-2012, 11:59:21 PM   #6
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Default Re: Found the culprit for differential failure (picture in here)

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Not the best pictures but this will work. You be the judge to the condition of mounts. Let me know If i miss something.
They appear fine in your pics. With the bolts removed from each bushing, can you induce flex easily with a pry device? Do you see cracks in the rubber when they finally do flex? If you can flex the bushings with a flathead with little effort, the diff bolts can obviously flex around that much easier.
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Old Thu, Apr-19-2012, 12:02:48 AM   #7
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Default Re: Found the culprit for differential failure (picture in here)

Tomorrow, I will inspect the bushings closely when the diff is out of the way. I also will test it.

I am really having some trouble taking off my remus exhaust. Just 2 freaking hanger. I don't even if it is safe to use PB blaster on rubber. Also its somewhat tight space.
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Old Thu, Apr-19-2012, 12:12:35 AM   #8
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Default Re: Found the culprit for differential failure (picture in here)

I do not see a pic of the front diff mount where you removed the bolt from, however the 4 subframe bushings appear to be PowerFlex Purples, a very popular poly bushing. The 2 rear diff mounts, well, you can not really see dry rot or cracking in photos. You will just have to take a good look at them and the front.

Bottom line, most of the time when that bolt breaks it is due to bad bushings. There are other causes, like the bolt backed out for example. If the PO changed out the subframe bushings he might have done the diff bushings as well. My point was you need to be sure before buttoning it all back up. I promise there are guys on here that run BIG HP numbers, so that alone is not the only possible cause.

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Old Thu, Apr-19-2012, 12:17:20 AM   #9
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Default Re: Found the culprit for differential failure (picture in here)

Quote:
Originally Posted by white-hot View Post
I do not see a pic of the front diff mount where you removed the bolt from, however the 4 subframe bushings appear to be PowerFlex Purples, a very popular poly bushing. The 2 rear diff mounts, well, you can not really see dry rot or cracking in photos. You will just have to take a good look at them and the front.

Bottom line, most of the time when that bolt breaks it is due to bad bushings. There are other causes, like the bolt backed out for example. If the PO changed out the subframe bushings he might have done the diff bushings as well. My point was you need to be sure before buttoning it all back up. I promise there are guys on here that run BIG HP numbers, so that alone is not the only possible cause.

Great info! I didnt realize that!

From what I saw, the front mount looks new. the bolt just snapped.

And I accidentally deleted my front diff mount where the bolt goes in when I was trying to upload. I pressed the wrong button.
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Old Thu, Apr-19-2012, 12:23:52 AM   #10
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Default Re: Found the culprit for differential failure (picture in here)

I talked with previous owner, he replaced all the bushings down there last year. Subframe and front diff mount. Thats why it looks new.
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Discussing Found the culprit for differential failure (picture in here) in the E36 M3 (1992-1999) Forum - {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999 at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)