Porsche discloses frequency of IMSB failures.
 

Through the class action lawsuits, the plaintiff's lawyers got Porsche to reveal the percentages of cars that experience IMSB failures. It looks like 996/986 single rows fail at around 4-10%, while the duoble row and 997s fail at less than 1%. Glad I have a double row!

IMS Class Action Suit 2001 through 2005 owners win Update Mar 12 - Page 2 - Rennlist Discussion Forums

I always wanted to be a 1%-er so looks like I got my wish. This is good info. There is absolutely no way I am going to touch the IMSB until I go in there anyway to do the clutch and, depending on what I find, I may not even do it then.

Actually that number -- 4 to 8% --, estimated by the plaintiffs' lawyers via Porsche documents and not an estimate directly form Porsche NA, is just for the compromised failures that Porsche made somewhat good on.

It doesn't include the compromised IMSB's that Porsche did nothing about, presumably out of warranty cars that they offered no charity to. And if you consider that an undetermined number of those single row bearing cars sold were low mileage cars during the warranty period, then it stands to reason that the IMS failures will exceed that 4-8% figure once those former garage queens/low milers start taking on daily driving duties under 2nd, 3rd owners.

The real trick is to determine how many single row bearing cars have not had their IMSB's upgraded even after having the clutch replaced. Remember, the LNE bearing is a fairly new preventative option (probably still in the single digit % of all single row cars out there) and the revised M97 bearing that went into some m96 engines...who knows what's up with those, Porsche isn't talking.

I read this a few days ago. The way it's laid out with the VIN's listed made me think the first percentage referred to the 986 and the second to the 996.

No idea if this is correct, just a possible interpretation of legal twaddle.

I have an '01 Boxster S. Arranged to have the IMSB replaced on the assumption that I probably had the single row. Of course, it's impossible to know until you remove the transmission, and as it turns out I have the double row. The labor is already a sunk cost and the bearing was already purchased, so I'm going ahead with the replacement; however if I had known I had the double row bearing, I would not have bothered with replacement.

Is there any way to know what bearing I have in my 1997 986?

Probably a single row bearing........
These bigger bearings were used untill 2000 & some early 2001 builds when Porsche again reverted to single row bearings. But removal of the transmission to inspect the bearing carrier is the only true way of knowing.

Porsche replaced my engine around 10K. Can't get the dealer to release the service records since I'm not the original purchaser. The car only has 20K, so I opted for the LNE bearing. The car went through several owners post engine failure and was a CA car. Given multiple owners and so few miles, I would surmise the ISMB is a bigger issue than we want to accept.

This is GREAT news for 1999 and older Boxster owners!!! It's my understanding that all 1999 and older Boxsters have the double bearings.


I have a 1998 with 27k miles and I really didn't want to drop the transmission if not absolutely necessary or before I need to replace the clutch.

This new information that Porsche has released makes me want to.....


:dance::dance::dance::dance::dance::dance::dance:: dance:




I wonder if the value of the older Boxters is going to increase do to this new information? I don't care, now that I can rest easier, I'm going to keep mine!

What exactly is the difference between a single and double row bearing? What makes a double row better than a single row?

Twice as many rows.

Is there any hard statistics to prove the LN bearing is any less prone to random failure than OEM? Have they been around long enough to really have an educated opinion or do we need more time? I assume my 02 S with 13,000 miles on the odometer is a single row and in the group more likely to fail - (low miles and single row = double whammy). I hate the thought of tearing into a mostly new motor and then wonder what other potential problems that can cause down the road, but I may do it anyway. I really don't worry about it too much anymore and I just enjoy the ride.

From what I have read, most failures were in low mileage cars (<30k). If it were my car, I would definitely get it replaced.

I share your thoughts on the LN bearing, it hasn't been around long enough to know if this is a permanent fix.

Porsches are like race horses, you need to run them hard once in a while. I once went thru a period where I garaged a couple cars of and on for 10 years, up to 2 years at a time, and they always seemed to have something wrong with them when I them back up.
Get those low mileage Boxster out of the garage and start driving. 27k on a 99? Who drive less than 2000 miles a year?

Well LNE is a privately owned company so they are not required to disclose their stats anymore than Porsche never did. But LNE have posted many times on various Porsche forums that they've sold well over 10,000 retrofit bearings with only a handful going down to defeat and those few were mostly due to improper installation or failures on engines that were already compromised -- owner must have heard something funny and tried to make amends too late.
They also state that they've not had a single LNE dual row bearing go down. Given that this is not an easy DIY, I think professional insallation would keep the numbers of correctly installed LNE bearings pretty high.
My own mechanic told me he's done about 400 at his is small shop where they're not rushing cars in and out.

The other thing too is that these forums are pretty hard to control if you're selling snake oil. If lots of folks were having their LNE bearings go down you'd be hearing about it pretty quickly. I can't recall reading about a single one on 986forum, Renntech or Rennlist. But I have read about dozens of factory IMS failures.
Granted the size of water-cooled Porsche owners who post on these forums is a fraction of the total.

My 2000 'S' had a mint condition double row in it when I took it out at 55k miles. Of course now I have an even sweeter LNE double row installed and never ever think about it.

Side note, my new 981 likes to run around in long gear 7th all the time in the 1400 to 2400rpm unless I'm having fun which is most of the time so far. Sure glad the bearing is gone now! :eek::cheers:

^ the 981 software likes to lug the engine in automatic mode?

The Boxster (or any roadster) is often a life style change car, both buying and selling. I know mine were, buying I had retirement paid for and the kids thru grad school. Selling I was not using the car, 50 miles from a mechanic and nearing 70. But often it is new job, marriage, moving, etc that triggers either buying of selling. I doubt 50% of the buyers for used Boxsters know what a IMS is.

Cars fall into several categories:

'97-'99 and too old for most to be worth doing a $2k preventative action or the owners are too financially challenged.
'00-'05.5 and falling into that 3 models old situation, still worth something, most 3 owner cars and less than 10% have done anything to the IMS and 80% are still on the original.
'05.5-'08 with the newest IMS design, just saw my first not covered by warranty report this week. Thought to be better but then we really won't know for 5 more years when all are out of warranty and the cost of a rebuild drives many to the boneyard because the cost of a wreck AND an IMS makes repair uneconomical.

Are their LN installation failures? Yes.

Are there a very very few unexplained LN failures that can't be attributed to installation or collateral damage? One or two out of perhaps 10k by now.

Are there a few LN bearings that have been taken out by the failure of another unconnected part failing and spewing metal through the engine that gets caught up in the LN bearing which is lubed with unfiltered oil? Yes, a few. (Why "The Solution" uses just filtered oil. And why all IMS failures aren't really caused by the IMS itself failing.)

Total for all causes around 1/10 of 1 % for LN last I checked versus 1% per car per year (my guestimate) for the OEM part (includes ones known to have failed and ones seen failing on removal).

So for the LN there are now thousands which have been driven several years, some over 50k miles. I think we are seeing some data that LN willingly shares to see the materials and lubrication method LN chose, while not perfect, are much better than the ones used in the cars from the factory. (Can you afford perfect?)

And LN recommends an inspection or replacement every 50k miles just to be safe.

Close, but as soon as it feels it doesn't have enough torque to service medium throttle request it will shift down. It is the only part of PDK I don't like, if it is not in sport mode it will not drop gears quick enough to satisfy a little increase in throttle, it doesn't lug but it sort of just does nothing (which I guess one could call lugging). It reminds me of the Tips in that the driver needs to learn to modulate their foot pressure to control down shifts.
Don't get me wrong PDK is still really nice but with a lower torque engine like the 2.7 it can at times be a little sluggish. If I drive it with any authority like most would it is a total non-issue. The interesting thing is with my 986 manual it is always driven with authority, for me getting a PDK was like being back in my Benz, I need to remember I’m in a Porsche and use the darn gas!