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Discussion Starter · #1 · (Edited)
First off my car is a 2000 M5 w/ 100,000+ Miles

OK, so I'm pretty sure I've found a post similar to the issue I just encountered (http://www.m5board.com/vbulletin/e3...7886-i-broke-my-rear-subframe-driveshaft.html):sad1::sad1:

It appears that the Rear Differential Mount that is welded to the Subframe has ripped apart. I'm amazed that this is an issue considering the performance of these cars. Noting that the post I came across is from 2004, I'm wondering if there is additional information regarding this issue?

Is it possible to simply order the Diff mount and have it welded in place of the defective part, or is it necessary to repalce the entire subframe??

Does anyone else have experience with this issue???????

Any info would be great.

 

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WOW! I am shocked.
 

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What were you doing when it happened? That seems like an uncommon problem for these cars.
Its not hard to believe. They have a weak aluminum subframe thats not designed to take abuse like burnouts/powersliding/axle hop. That type of stuff will destroy the subframe. Consider it a known weakpoint as Dinan addressed this with their subframe reinforcement on the S3 Package. It would be nice if we could get a recall like on the E46's
 

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This is a notoriously weak link of the E39 M5. Take the car to a Dinan authorized service center and have it welded together with the Dinan subframe reinforcement kit.

--Peter
 

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Discussion Starter · #6 ·
This is a notoriously weak link of the E39 M5. Take the car to a Dinan authorized service center and have it welded together with the Dinan subframe reinforcement kit.

--Peter

I've read about the reinforcement kit. I'm curious if the mount can be purchased seperately and welded to the subframe in conjunction with the kit? Or is a new subframe essential? As far as I can tell (and I will examine further) the break appears to have only been at the mount. If that is so, it's conceivable that the old one can be removed and the new one welded in it's place. But I know nothing about welding, and in particular, aluminium.

Although I've gotten on the car a bit since I've owned it, it's not excessive and normally at a rolling start. I don't jump on it from a stand still. These cars are designed for the Autobahn not the dragstrip.
 

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I've read about the reinforcement kit. I'm curious if the mount can be purchased seperately and welded to the subframe in conjunction with the kit? Or is a new subframe essential? As far as I can tell (and I will examine further) the break appears to have only been at the mount. If that is so, it's conceivable that the old one can be removed and the new one welded in it's place. But I know nothing about welding, and in particular, aluminium.

Although I've gotten on the car a bit since I've owned it, it's not excessive and normally at a rolling start. I don't jump on it from a stand still. These cars are designed for the Autobahn not the dragstrip.
Probably can do that, but you also can track down a new subframe or a good used one on eBay pretty cheaply. Literally, I saw a new one recently for very low dollars on eBay.

--Peter

Link to a used one on eBay for $450 buy it now: http://cgi.ebay.com/ebaymotors/01-B...Q5fTruckQ5fPartsQ5fAccessories#ht_2830wt_1167

The new one on eBay was $325, but is for the front.
 

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. They have a weak aluminum subframe thats not designed to take abuse like burnouts/powersliding/axle hop. That type of stuff will destroy the subframe.


Consider it a known weakpoint as Dinan addressed this with their subframe reinforcement on the S3 Package. It would be nice if we could get a recall like on the E46's


1. By your comment you say it is "weak" because it is not desgined to take ABUSE!!!! Look up the definition of abuse.

2. burnouts/powersliding/axle hop are all outside the normal realm of adult drivers. These have nothing to do with the intended use of an M5, IMHO.

3. A DINAN S3 is not a stock M5. There is a REASON they address the subframe when increasing power.

4. If this was a 'known' weakpoint that was worthy of recall, maybe there would be more than a handful reported over the last 10 years....
 

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1. By your comment you say it is "weak" because it is not desgined to take ABUSE!!!! Look up the definition of abuse.

2. burnouts/powersliding/axle hop are all outside the normal realm of adult drivers. These have nothing to do with the intended use of an M5, IMHO.

3. A DINAN S3 is not a stock M5. There is a REASON they address the subframe when increasing power.

4. If this was a 'known' weakpoint that was worthy of recall, maybe there would be more than a handful reported over the last 10 years....

1. It is weak, in my opinion its poorly designed, in hindsight it should be able to take everything you throw at it. Maybe i shouldnt say abuse, its not the right word i was looking for.

2. Yes those may be out of the realm of most normal drivers, but look at it this way, the M5 is considered a sports sedan, people tend to buy cars like that because they still like the idea of a fast car thats still able to have fun but be practical at the same time. I didnt buy my M to do burnouts, powerslide around corners, or anything like that, but you have to look outside yourself and other drivers. Why bother buying an M5 if your going to drive it like a grandma, many will agree these cars werent designed to drive slow, they were designed to be driven spiritedly, peoples definition of spirited driving will differ. Im willing to put money on it more than half this board has done a burnout at one time or another. Anyone whos run their M5 at the drag strip, anyone whos done hard launches which have resulted in some wheel hop or whatever is testing the subframe. The car was designed to be driven fast, it was marketed to be driven hard, its not like this car came with 200hp and everyone on here is spraying a 200 shot nitrous or supercharging their M5's and complaining about it.

3. Yes thats true, an S3 is not a stock M5, but hey, thers been reports of STOCK m5's cracking subframes. This kinda ties in with #4. How many E39 owners do their own work on there cars? How many of them have them on a lift and have the luxuries of inspecting the rear subframe for cracking. Not too many, id say there are quite a few DIY'ers here but many of them do not throw their car on jackstands and stare at the underneath of the car unless there is an underlying issue. I think if more people inspected the subframes there would be a lot more cases of cracking subframes. Im not saying every other person is going to have a mount point ripped completely off, but i think the reported number of cases would rise.

4. I said it would be nice if it was a recall like the E46's. Obviously its not going to happen, but its nice to wish. I wouldnt say its a big problem because as its been noted, there are not that many reported cases. Remember though, a lot of the M5's are still not even at the 100K mark yet, id say the average on the board seems to be arond the 60-80K range.

Dont mean to come off as a dick, but the point i was trying to prove is, the subframe is weak from one point of view. These subframes arent designed to take abuse, the M5 was never designed to do burnouts, but its something that they should have known was going to happen.
 

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Dont mean to come off as a dick, but the point i was trying to prove is, the subframe is weak from one point of view. These subframes arent designed to take abuse, the M5 was never designed to do burnouts, but its something that they should have known was going to happen.
Me neither, but if this was a true problem we'd hear a lot about it.

A $80k 'sports sedan' is not meant to be powerslid or drag raced. I drive in triple digits on 2 lane 'barely divided' roads on a day in day out basis- hard road racing, driving way to fast, drifting corners, hard acceleration and peak braking- but not abuse.

I am tired of manufacturers being held responsible for all the stupidity of their customers....

:)

A
 

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Me neither, but if this was a true problem we'd hear a lot about it.

A $80k 'sports sedan' is not meant to be powerslid or drag raced. I drive in triple digits on 2 lane 'barely divided' roads on a day in day out basis- hard road racing, driving way to fast, drifting corners, hard acceleration and peak braking- but not abuse.

I am tired of manufacturers being held responsible for all the stupidity of their customers....

:)

A

I definately understand where your coming from. In an ideal world, the subframe would come reinforced, but hindsight is always 20/20. I didnt mean to make it sound like its a huge problem plauging all E39's, its definately something that is more common in vehicles who were abused/driven past their limits. Its one of those things though, BMW knew exactly what people were going to do with the M5, its not like people are buying 525/530 drag racing them, cracking subframes them coming after bmw for a poor design. The M5 is what it is, i think with the younger crowd of new owners subframe damage may be on the rise given how "most" younger people drive.

I can proudly say, ive only done 2 actual burnouts, one at a drag strip the other just because i could. Aside from that, ive never done them, dont really see the point in burning off brand new tires and causing havoc on my subframe/diff/axles/driveshaft/tranny/mounts/tires. Sometimes its hard not to get spin though, i find first and secon gear are kinda useless at times even in the dry :M5launch:
 

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Discussion Starter · #12 ·
Probably can do that, but you also can track down a new subframe or a good used one on eBay pretty cheaply. Literally, I saw a new one recently for very low dollars on eBay.

--Peter

Link to a used one on eBay for $450 buy it now: 01 BMW E39 M5 Rear Aluminum Diff Subframe Cross Member : eBay Motors (item 250522193465 end time Feb-26-10 17:43:41 PST)

The new one on eBay was $325, but is for the front.
Thanks for the heads up on this part. I also saw it on Ebay. Considering the Damage though, I'm a little skeptical about purchasing a used subframe. I still need to inspect mine more throughly to verify that this was the only stress point/fracture.

Can anyone tell me the technical name of the actual rear diff mount or dampener that broke? Maybe a part number? I think if I can acuire it, that I may be able to have it TIG welded up. In the mean time I guess I can call the dealership eh??
 

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Discussion Starter · #13 ·
The other thing that bothers me about some of the posts is this issue that these cars aren't designed for certain types of hard driving. A "tuned" car that costs $80,000 new, should be designed above and beyond anything that is thrown at it in terms of driving. Even if it is a "Sport Sedan". It's simply absurd that this is an issue. You would think in order to acheive this break I'd have to be on it all the time, the entire time I'm driving. And that simply isn't the case. The occasional burnout shouldn't cause structural tearing like this. The engineers knew full well the perfomance capabilities of these vehicles and should have designed mounting points to acheive better than average performance. I'm curious if this is an issue with Benz or Porsche. BTW, has anyone seen the BMW commercial/movie with Madonna in it (http://www.youtube.com/watch?v=srrbvNNUKrA ) that was used to market this car? I don't come close to driving like that. So for those who argue that the dealer shouldn't be responsible for the habits of owners, I agree. However, then don't market the vehicle as an extreme performance machine if it isn't. Maybe the dealer should've had a grandmother driving it to the grocery store for milk instead. Maybe that would have been more appropriate. On the other hand, if it is a performance machine then design as such.
 

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The other thing that bothers me about some of the posts is this issue that these cars aren't designed for certain types of hard driving. A "tuned" car that costs $80,000 new, should be designed above and beyond anything that is thrown at it in terms of driving. Even if it is a "Sport Sedan". It's simply absurd that this is an issue. You would think in order to acheive this break I'd have to be on it all the time, the entire time I'm driving. And that simply isn't the case. The occasional burnout shouldn't cause structural tearing like this. The engineers knew full well the perfomance capabilities of these vehicles and should have designed mounting points to acheive better than average performance. I'm curious if this is an issue with Benz or Porsche. BTW, has anyone seen the BMW commercial/movie with Madonna in it (http://www.youtube.com/watch?v=srrbvNNUKrA ) that was used to market this car? I don't come close to driving like that. So for those who argue that the dealer shouldn't be responsible for the habits of owners, I agree. However, then don't market the vehicle as an extreme performance machine if it isn't. Maybe the dealer should've had a grandmother driving it to the grocery store for milk instead. Maybe that would have been more appropriate. On the other hand, if it is a performance machine then design as such.
Are you the original owner of the car? If not, you have no idea what sort of issue(s) this car experienced in its life. Perhaps some prior owner just powered through wheel-hopping burnouts on a daily basis. Perhaps the diff mount was worn in the past as he/she just axle hopped it off the line every chance possible. Perhaps it was improperly jacked at some point creating a stress crack which then propagated with time to failure. Etc. There could be many reasons for the outcome.

Like ard said though, this is a profoundly rare situation, so jumping to the conclusion that it is a design fault is not warranted imo. Also, your situation is nothing similar to the E46 situation which is not the subframe at all on that car but the unibody mounting points for the rear subframe that were the problem mainly on early production E46s (1999, 2000).

Chuck
 
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Discussion Starter · #15 ·
Are you the original owner of the car? If not, you have no idea what sort of issue(s) this car experienced in its life. Perhaps some prior owner just powered through wheel-hopping burnouts on a daily basis. Perhaps the diff mount was worn in the past as he/she just axle hopped it off the line every chance possible. Perhaps it was improperly jacked at some point creating a stress crack which then propagated with time to failure. Etc. There could be many reasons for the outcome.

Like ard said though, this is a profoundly rare situation, so jumping to the conclusion that it is a design fault is not warranted imo. Also, your situation is nothing similar to the E46 situation which is not the subframe at all on that car but the unibody mounting points for the rear subframe that were the problem mainly on early production E46s (1999, 2000).

Chuck
As I stated somewhere in this post the car came to me with about 80,000 miles on it. Obviously I can't account for the history from that point back.

And contrary to your opinion on this being rare, I've found several posts concerning the same issue with E39 M5s. Although it varies from the E46's mounting point problem, I think it's worth noting as a related problem with the design in this area of the car. Obviously utilizing aluminium in this manner has created problems that could have otherwise been avoided had these points been reinforced :lightbulb:(Hence the Dinan reinforcement Kit, now sold seperately 5 Series :: M5 (E39) 2000-2003 :: Chassis Tuning :: Rear Subframe/Differential Reinforcement Kit - Huh, why is that?? :confused2) or a other metal used. It seems a little to coincidental, but I'm no engineer.

Regardless, this has become an interesting discussion, none of which has answered any mechanical questions I had. :M5launch:
 

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Only a profoundly small handful of cars have had this issue in 10+ years -- I refer to that as rare. My background is in mechanical engineering, so I guess I look at things a bit differently perhaps. Anyway, the Dinan reinforcement was developed for the S3 which increases horsepower by over 50% and torque by ~40% compared to stock. At those levels of stress, something additional is needed to reinforce the subframe (i.e. reduce the cyclic stress level as cyclical stress levels beyond the endurance limit of a material is where fatigue failures are created).

Replace the subframe, add a new differential mount, and I'd do fresh subframe bushings and also rear ball joints, etc, while the whole thing is apart. You'll never have an issue again most likely.

Regards,
Chuck
 

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Discussion Starter · #18 ·
Only a profoundly small handful of cars have had this issue in 10+ years -- I refer to that as rare. My background is in mechanical engineering, so I guess I look at things a bit differently perhaps. Anyway, the Dinan reinforcement was developed for the S3 which increases horsepower by over 50% and torque by ~40% compared to stock. At those levels of stress, something additional is needed to reinforce the subframe (i.e. reduce the cyclic stress level as cyclical stress levels beyond the endurance limit of a material is where fatigue failures are created).

Replace the subframe, add a new differential mount, and I'd do fresh subframe bushings and also rear ball joints, etc, while the whole thing is apart. You'll never have an issue again most likely.

Regards,
Chuck

Thanks for the input, the whole ordeal has me stressed. :eek:h: This is no small repair.
 

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Aluminum breaks. Simple as that.

Aluminum has a fatigue/break point no matter what, unlike steel.

If you flex a piece of steel before the point where you bend it (meaning not bend it to the point where it wont go back) you will never fatigue or break it unless it corodes.

If you do this to aluminum, even though you are only bending it so it still returns to its original shape you are destroying the makup of the aluminum and at some point, however many cycles later, it will break.

So, when you look at these aluminum suspension pieces that have forces acting upon them, they have a life span, in most cases we will never see the end of the life, but in rare cases we will.

The M5 has enough weight and power to accelerate this degradation. If BMW would have over built every point of fatigue to last as long as steel, they just would have used steel and we'd have a 5000lb pig instead of 'only' 4000lbs.

Its the downside of aluminum for sure.

Bob
 

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Aluminum breaks. Simple as that.

Aluminum has a fatigue/break point no matter what, unlike steel.

If you flex a piece of steel before the point where you bend it (meaning not bend it to the point where it wont go back) you will never fatigue or break it unless it corodes.

If you do this to aluminum, even though you are only bending it so it still returns to its original shape you are destroying the makup of the aluminum and at some point, however many cycles later, it will break.

So, when you look at these aluminum suspension pieces that have forces acting upon them, they have a life span, in most cases we will never see the end of the life, but in rare cases we will.

The M5 has enough weight and power to accelerate this degradation. If BMW would have over built every point of fatigue to last as long as steel, they just would have used steel and we'd have a 5000lb pig instead of 'only' 4000lbs.

Its the downside of aluminum for sure.

Bob
Whoa!! Completely false. Steel ABSOLUTELY is susceptible to fatigue failure just like aluminum. No difference at all other than the stress limits that any given material will yield at. Either material will fail in fatigue if the stresses it sees in use are beyond the "endurance limit" (mech eng term -- investigate it) of the material. No difference. You simply account for this when you design a part by using the proper cross-section/thickness/geometry for the part depending on the material to be used. There is a wide range of aluminum and steel materials, each with slightly different mechanical properties, so you have to take the specific material to be used into account at the very beginning of the design. This is really basic mechanical engineering -- long proven science.

You can easily design an aluminum part to have infinite life in service just like you can a steel part. Of course the question every engineer is asking are what are the maximum cyclical and maximum static loads a given part will see in service. Then a "factor of safety" is added to those calculations (factors of safety multiples vary greatly depending on the part design and expected usage) to account for the expected but unknown conditions beyond the estimated service environment. This was all done on that rear subframe. It was designed to see infinite life in service. It will see infinite life in service unless it is subjected to loads beyond those expected when designed. Somewhere in the life of this car, the loads it experienced could have yielded the material for example (stressed a portion of it beyond the elastic limit) creating a stress concentration. Then when seeing continued usage from that point forward, the normal design cyclic stresses created the failure. There are other possibilities too of course of what led to this failure, so that's just an example.
 
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