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      11-14-2011, 05:20 PM   #89
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35 nm or 26 ft/lbs for the nuts on the exhaust bracket.

And yes, it appears that the diff itself is threaded for the bolts, and the nuts just hold the exhaust bracket in place.

I don't have my car to take any pics right now but I will try to in the next couple of days.
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      11-14-2011, 08:13 PM   #90
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^ thanks for the update, guess i will have to get under there and check again this weekend. Just to confirm, the 2 smaller differential bolts (tighting from the front) would be 100 NM, while the 2 nuts on the rear that holds the exhaust bracket are at 35 nm?
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      11-17-2011, 06:39 PM   #91
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Bolts on diff snapped again it appears

Was driving today when a quick shift to 2nd and hard acceleration caused the "thud" again. A look under the car showed the diff angled to the left touching the exhaust. I couldn't slide all the way under to verify it was the bolts once again but dealer has the car and will let me know. This has happened now less than 500 miles after they replaced the subframe and bolts. Will let you know what they find.

Update*. Dealer says same bolt(s) snapped again so factory rep is scheduled to come and look at the car next week.

Update #2: The car was looked at, damage noted, and dealer is awaiting parts to perform repair. So this is the 2nd time now within 500 miles of last snap.

Last edited by aussie2u; 12-04-2011 at 08:46 PM.
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      12-14-2011, 12:05 PM   #92
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my car just had the same problem and they are telling me BMW is not covering it because they are blaming it on abuse. Any suggestions?
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      12-14-2011, 12:30 PM   #93
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popping like back firing?
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      12-14-2011, 12:55 PM   #94
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Quote:
Originally Posted by FastM3 View Post
my car just had the same problem and they are telling me BMW is not covering it because they are blaming it on abuse. Any suggestions?
Did you abuse it? How did it happen?

If you are innocent, get an attorney.
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      12-14-2011, 01:16 PM   #95
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Quote:
Originally Posted by aussie2u View Post
Was driving today when a quick shift to 2nd and hard acceleration caused the "thud" again. A look under the car showed the diff angled to the left touching the exhaust. I couldn't slide all the way under to verify it was the bolts once again but dealer has the car and will let me know. This has happened now less than 500 miles after they replaced the subframe and bolts. Will let you know what they find.

Update*. Dealer says same bolt(s) snapped again so factory rep is scheduled to come and look at the car next week.

Update #2: The car was looked at, damage noted, and dealer is awaiting parts to perform repair. So this is the 2nd time now within 500 miles of last snap.
Which side snapped the first time, the right side or the left, and did they replace both when it happened the first time?
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      12-14-2011, 01:41 PM   #96
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Quote:
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Which side snapped the first time, the right side or the left, and did they replace both when it happened the first time?
good question!
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      12-14-2011, 02:13 PM   #97
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Just got the car back. They replaced the bolts again and installed new diff just to make certain something inside wasn't locking up and causing it.

I feel the repairs were made under a bit of goodwill as the car is perfect, completely stock, still has original tires with lots of tread left with 14k miles on it now.

They replaced the bolts, another complete subframe, and installed a re manufactured differential to make sure something wasn't binding. Remember that the car performed flawlessly for 13k miles and then when the first set of bolts snapped, it happened again within 500 miles of the repair. So I'm being told with everything now replaced, "it better not happen again..."

The torque on these bolts must be enormous when the clutch and tires do not slip at all. I wouldn't attempt to drag the car, thats for sure. I'll now rethink the some of the high rpm, sudden "on/off" throttle movements as that surely must stress those things. I saw a picture of the subframe bolt hole and it was wallowed out by movement. I think once it gets enough "play", it just snaps. Thats my opinion, dealer didn't say.

Good luck all!
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      12-14-2011, 02:17 PM   #98
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Quote:
Originally Posted by Richbot View Post
Which side snapped the first time, the right side or the left, and did they replace both when it happened the first time?
If I remember correctly, right side snapped first. I assume each bolt was replaced as a new subframe was installed.

Curiously, dealer did mention that my 2011 did not have holes completely tapped for the bolts all the way to the ends. Hope that description makes sense but when I looked at the pic, the threads did not extend all the way to the surface, but stopped maybe 1/4" in. Dealer evidently checked another new model to see if this was correct and it now is.
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      12-14-2011, 02:21 PM   #99
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Quote:
Originally Posted by FastM3 View Post
my car just had the same problem and they are telling me BMW is not covering it because they are blaming it on abuse. Any suggestions?
I don't have any suggestions other than have a factory rep look at it. If the car is stock and no obvious signs of abuse, I would think it should be covered. It sounds like the BMW factory rep is making the call though as I had to wait 2 weeks until he could come and view it.

Best of luck
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      12-15-2011, 07:35 PM   #100
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they said they sent photos to BMW of N/A and then they said it was abuse.
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      12-21-2011, 07:04 PM   #101
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Have you looked into swapping the stock rubber mounts for VACs solid ones..that will eliminate any broken bolts caused by torque twist..

http://store.vacmotorsports.com/vac-...kit-p2217.aspx
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      12-23-2011, 07:41 AM   #102
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Quote:
Originally Posted by tibra1 View Post
Have you looked into swapping the stock rubber mounts for VACs solid ones..that will eliminate any broken bolts caused by torque twist..

http://store.vacmotorsports.com/vac-...kit-p2217.aspx
Also interested to see if anyone has installed these.
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      12-23-2011, 12:08 PM   #103
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Quote:
Originally Posted by tibra1 View Post
Have you looked into swapping the stock rubber mounts for VACs solid ones..that will eliminate any broken bolts caused by torque twist..

http://store.vacmotorsports.com/vac-...kit-p2217.aspx
Exactly! I have been saying this for a long time. These bushings along with the axle carrier bushings need to be upgraded.

The soft bushings paired with the "shock intensive" drive train of this M3 are a bad combination.

THe differential and subframe bushings a must.
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      12-23-2011, 03:20 PM   #104
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I realize BMW tries to balance ride noise/comfort with performance..but these should have came from the factory with solid mounts...ESPECIALLY on an M car..very disappointing..re-inforcing this is going to be my first mod.
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      12-27-2011, 08:52 AM   #105
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Got me paranoid so I check the diff and everything looks like it is mounted properly. Luckily I installed the exhaust myself and didn't do the shortcut with the hangers. Will someone get those solid bushings already and report back? Seems like something worth getting down the road!
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      12-27-2011, 09:00 AM   #106
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Quote:
Originally Posted by armyav8tor View Post
Got me paranoid so I check the diff and everything looks like it is mounted properly. Luckily I installed the exhaust myself and didn't do the shortcut with the hangers. Will someone get those solid bushings already and report back? Seems like something worth getting down the road!
Per Malekreza, those hangers for the exhaust are not relevant to this failure. This was a misunderstanding by myself and others here. This failure happens on 100% stock cars.
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      01-08-2012, 10:43 PM   #107
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Reporting back. Finally got to work on this. As pointed out by the posters above, the 2 nuts for the exhaust hangers do not support the diff.

I have to remove the exhaust and the heat shield to get solid contact on the 2 bolts from the front. They were definitely under torqued and not at 100 NM. Should be good now though. Thank you guys for all the information and knowledge.
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      03-23-2012, 10:59 AM   #108
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Quote:
Originally Posted by e92zero View Post
Reporting back. Finally got to work on this. As pointed out by the posters above, the 2 nuts for the exhaust hangers do not support the diff.

I have to remove the exhaust and the heat shield to get solid contact on the 2 bolts from the front. They were definitely under torqued and not at 100 NM. Should be good now though. Thank you guys for all the information and knowledge.
So does installing an aftermarket exhaust by removing those two nuts (rather than removing the exhaust from the rubber hangers) have any effect on this as many have thought?
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      03-23-2012, 11:08 AM   #109
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So does installing an aftermarket exhaust by removing those two nuts (rather than removing the exhaust from the rubber hangers) have any effect on this as many have thought?
No.
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      03-23-2012, 12:58 PM   #110
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my question is how do you get a torque wrench in there. the head of mine is too big.
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