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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 Thu, Apr-19-2012, 01:49:18 AM   #11
fiveightandten
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Default Re: Found the culprit for differential failure (picture in here)

That diff cover has been replaced, so it doesn't surprise me that the bushings are ok in the back. If he says he replaced the front diff mount, I don't have any reason to doubt it, but that's usually the cause of broken bolts.

IMO, the temperatures have not been high enough, nor do your tires have enough grip to put enough stress to break a fresh bolt sitting in a fresh mount. But who cares at this point what caused it. Replace the necessary parts so it won't happen again.

What is it about the diff that's blown? The car will make horrible noises with a broken front diff bolt, as the diff will be rattling around in the sub frame smacking against the metal. Are you sure there's something wrong with the internals? Did you spin it by hand or take the cover off to have a look inside?

Also, as a side note...with that aftermarket rear sway, i'd highly recommend getting some reinforcement tabs welded into the mounting points.

Whatever diff goes back into the car:
-New mounts all around
-Bimmerworld upgraded bolt

EDIT: Also, i'd recommend dropping the exhaust/heat shield, and confirming that your center support bearing surround isn't torn now. Have a hard look at the giubo (flex disc) too.
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Last edited by fiveightandten; Thu, Apr-19-2012 at 01:54:50 AM.
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Old Thu, Apr-19-2012, 01:58:19 AM   #12
DEAFM3
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Default Re: Found the culprit for differential failure (picture in here)

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Originally Posted by fiveightandten View Post
That diff cover has been replaced, so it doesn't surprise me that the bushings are ok in the back. If he says he replaced the front diff mount, I don't have any reason to doubt it, but that's usually the cause of broken bolts.

IMO, the temperatures have not been high enough, nor do your tires have enough grip to put enough stress to break a fresh bolt sitting in a fresh mount. But who cares at this point what caused it. Replace the necessary parts so it won't happen again.

What is it about the diff that's blown? The car will make horrible noises with a broken front diff bolt, as the diff will be rattling around in the sub frame smacking against the metal. Are you sure there's something wrong with the internals? Did you spin it by hand or take the cover off to have a look inside?

Also, as a side note...with that aftermarket rear sway, i'd highly recommend getting some reinforcement tabs welded into the mounting points.

Whatever diff goes back into the car:
-New mounts all around
-Bimmerworld upgraded bolt

EDIT: Also, i'd recommend dropping the exhaust/heat shield, and confirming that your center support bearing surround isn't torn now. Have a hard look at the giubo (flex disc) too.
I have reinforcement tabs already welded for sway bar. Previous owner knew what he was doing. The mounts are barely a year old.

I will look into that. Just need to work on hanger bolts to loosen up. I suspect that popping the clutch and sudden shock caused the diff bolt to break. I had trouble starting up when I recently received the car. Plus the lightweight flywheel, My brother tends to let go the clutch lot quicker so it would grab lot harder. Stage 3 clutch is very grabby clutch.

EDIT: do you mean dropping almost whole exhaust system? I am having hard time to loosening up the hanger bolts as the rubber moves around some.
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Last edited by DEAFM3; Thu, Apr-19-2012 at 02:05:57 AM.
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Old Thu, Apr-19-2012, 02:22:35 AM   #13
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Default Re: Found the culprit for differential failure (picture in here)

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Originally Posted by DEAFM3 View Post
I have reinforcement tabs already welded for sway bar. Previous owner knew what he was doing. The mounts are barely a year old.

I will look into that. Just need to work on hanger bolts to loosen up. I suspect that popping the clutch and sudden shock caused the diff bolt to break. I had trouble starting up when I recently received the car. Plus the lightweight flywheel, My brother tends to let go the clutch lot quicker so it would grab lot harder. Stage 3 clutch is very grabby clutch.

EDIT: do you mean dropping almost whole exhaust system? I am having hard time to loosening up the hanger bolts as the rubber moves around some.
You may be able to get your head up there with the diff out of the car. If you need to get the exhaust down, just pull the bolt out that hold the mounts into the body. 13mm deep socket. The hard part are the front bolts at the triangle flanges where the pipe meets the headers. Though, you can also separate the pipes.

It's not a huge concern. But i'm looking at your diff with no front bolt and it's not sitting on the sub frame. Something has to be holding it up...the rear mounts, and the center support bearing.

There are no rear sway bar reinforcements in those pictures.
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Old Thu, Apr-19-2012, 03:02:40 AM   #14
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Default Re: Found the culprit for differential failure (picture in here)

maybe I am looking at wrong reinforcements something in my head. Is it that important to have them in there?

The diff sat/leaned into the front diff mount. That mount bracket probably held the diff up.
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Old Thu, Apr-19-2012, 03:13:29 AM   #15
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Default Re: Found the culprit for differential failure (picture in here)

The reason the bolts break is due to wheel hop, Unfortunately these cars wheelhop like crazy and any time the suspension load and unloads like that it will snap that bolt. If you can cure wheelhop, you will stop snapping bolts.
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Old Thu, Apr-19-2012, 03:18:43 AM   #16
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Default Re: Found the culprit for differential failure (picture in here)

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The reason the bolts break is due to wheel hop, Unfortunately these cars wheelhop like crazy and any time the suspension load and unloads like that it will snap that bolt. If you can cure wheelhop, you will stop snapping bolts.
So how did you cure the wheel hop? What makes our cars wheel hops?
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Old Thu, Apr-19-2012, 09:54:37 AM   #17
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Default Re: Found the culprit for differential failure (picture in here)

1) your flywheel has nothing to do with you breaking the diff bolt
2) it has everything to do with a bad front diff bushing. You did not post a picture of the diff bushing, and I would be willing to bet that it wasnt changed, or is beat
3) wheel hop does kill diff bolts. Why you drag launching the car anyways?
4) if u have an upgraded front diff bushing (AKG 75D), and an upgraded diff bolt... ENJOY
5) you need to re-evaluate why it broke, and INSPECT
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Old Thu, Apr-19-2012, 11:54:45 AM   #18
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Default Re: Found the culprit for differential failure (picture in here)

It broke because of driver abuse...lol

2 choices, buy a diff support brace from Active Auto, or weld in Mike Redowski's brace. Done!
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Old Thu, Apr-19-2012, 12:39:56 PM   #19
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Default Re: Found the culprit for differential failure (picture in here)

Quote:
Originally Posted by OahuMPower View Post
1) your flywheel has nothing to do with you breaking the diff bolt
2) it has everything to do with a bad front diff bushing. You did not post a picture of the diff bushing, and I would be willing to bet that it wasnt changed, or is beat
3) wheel hop does kill diff bolts. Why you drag launching the car anyways?
4) if u have an upgraded front diff bushing (AKG 75D), and an upgraded diff bolt... ENJOY
5) you need to re-evaluate why it broke, and INSPECT
Well this car is first standard car.

I am goin to take picture of front diff bushing.

I don't drag my car, I never floor in first, always do progressively during the acceleration.

I'm pretty sure my front diff mount are stock rubber but I'll look into now.
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Last edited by DEAFM3; Wed, Sep-12-2012 at 11:45:51 PM.
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Old Thu, Apr-19-2012, 12:45:16 PM   #20
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Default Re: Found the culprit for differential failure (picture in here)

Don't weld the Mike Radowski diff support.... not worth it. AA DSB is a well made piece, but honestly Cal and Nick are right - with a new AKG front diff bushing in there and the correct bolt, there is no reason it should snap. I beat the living piss out of my car and mine has never broke.

Also, Nick is right again, you do not have sway bar reinforcements and yes they are important if you don't want to tear the subframe ears out.
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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)