11 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHseperate thread on secondary IMSB failures?
Leading reported evidence
Install by a competent mechanic
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed · Original poster
Luckily, it is not my car, mine is humming along nicely with a new clutch and a new ceramic LN dual row bearing installed by a competent mechanic using the right tools.
Leading evidence: 'Install by a competent mechanic' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check every shaft' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
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Suggestion
We check every shaft before pinning and replacing the bearings - anything over .005" runout we fail.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
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Suggestion · Original poster
There was not too long ago a conversation on a IMSB failure AFTER replacing the bearing.
Replace bearings - anything over .005" runout we fail
Suggestion or failed attempt
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
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Suggestion
We check every shaft before pinning and replacing the bearings - anything over .005" runout we fail.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
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Suggestion · Original poster
The car was driven regularily after replacement and had regular inspections and oil changes by a Porsche dealer.
Discussions that performed work without a confirmed outcome
1
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0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
Luckily, it is not my car, mine is humming along nicely with a new clutch and a new ceramic LN dual row bearing installed by a competent mechanic using the right tools.
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
Luckily, it is not my car, mine is humming along nicely with a new clutch and a new ceramic LN dual row bearing installed by a competent mechanic using the right tools.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
11 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T225432Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
There was not too long ago a conversation on a IMSB failure AFTER replacing the bearing. This was a case 35.000km (20k miles?) after replacement. Fingers pointed to LN Engineering. I checked out the case and it appears this failure was with a none-ceramic single row bearing from LN. I remember these were available earlier? The car was driven regularily after replacement and had regular inspections and oil changes by a Porsche dealer. The engine will be taken apart further in coming weeks but until now all points to a bearing or shaft failure.
My point is that this is the biggest fear of many; spending the money or purchasing a car with IMSB done and then it fails. Can we collect some documented cases of such failures? I think we all are familiar with some of the 24 modes of failure of an M96 and I for one believe often fingers are pointed to IMSB failure while the actual failure mode is/could be another one. But still, if they do, why do they fail?
If I recall correctly (might be wrong) that car had an undisclosed (disclosed later) rear end crash that could have damaged something in the engine, leading to eventually failure after some miles were put on.
Also it was not clear what actually caused the engine meltdown, too much overall damage to pinpoint the IMS as the fault.
Its worth bearing(sic) in mind that case and IM shaft runout is one of the factors at play with IMS fails. If the engine runout is bad, swapping to a better bearing won't fix that problem.
My car had 102k miles on the OEM IMS bearing and it was almost perfect, so my runout must be good.
The runout problem might be one of the reason Porsche on the 997 moved the IMS bearing location to the internal portion of the engine which made it inaccessible from the flywheel side. Perhaps they felt during manufacture they could control it better by machining from the reverse side?
I've carried out a runout survey and found huge variations in shafts. We check every shaft before pinning and replacing the bearings - anything over .005" runout we fail. The highest we've seen is .020".
The late 06-08 shafts have the most consistent bearing housing bores.
Thank you Charles !
Honestly, how many of us who have diligently rebuilt an M96 had the runout/OOR etc measured? We did not have any specs to follow,had no procedure. We did not even hear the first mention of the issue until relatively recently in the decade+ long IMSB saga.
So thanks to LN for raising the issue. Very helpful.
Correction. Worst IMS had .028" of runout.
I uploaded a few of the photos from my analysis done a while back for those interested:
https://www.dropbox.com/sh/jysa8bfih...nSeD00yza?dl=0
Wow ,so run-out measurement locations are :
1. the tube
2. the base of all the gears
3. the extreme end of the gear assy.
Interesting that an IMS tube with only 2 thou run-out can have a gear with 28 thou ! see photo #16 - if I am reading correctly?
How long would the bearing in that tube last? Yikes.
Hard to be sure how long a bad one would last - certainly don't want to try! Some of these shafts came in to us with wear or bearings in process of failing.
The way the IMS is made, there are a bunch of parts that are all swedged together onto a pipe without any key ways - just a press fit.
An example of dimensional stack-up at its finest.
Thanks Charles for the clarification. Luckily, it is not my car, mine is humming along nicely with a new clutch and a new ceramic LN dual row bearing installed by a competent mechanic using the right tools. Thanks for your work on this subject and your feedback in this thread.
To Chris (MA): no, this is a seperate instance.
This is a source reference. Confirm exact model applicability in the original material.
