What years used the dual row IMSB?

Happy Sunday, Changed the oil for the first time since buying the 2000 996 cab 6-speed 2 weeks ago (low 27,000 miles.) No glitter in the oil, and none in the oil filter pleats that I cut open. When I first bought it, I thought for certain I would immediately have the IMSB upgraded. However, the more reading I do, I�m considering not doing it till new clutch or whatever. It seems the odds of bearing failure or pretty low, especially on the dual-row models. A fellow Rennlister tells me that mine is the dual-row version (built 11-99). Having said that, I�m not finding search answers for my question: can someone tell me when the dual-row bearings were used? Thank you. -Jim

I haven't seen any firm answers on that but I know that my build date 01/00 has a double-row. Even some 2001's have double row bearings.

My 2000 has a build date of 11/4/99 and never an IMSB problem at 93,000 miles. I have most, but not all paperwork going back to new and no mention of it being replaced.

I believe that MY1998,1999,2000 have the double row bearing.

The experts that have posted on this site have stated that the MY1999 are all dual row (assuming they have their original engines). The MY2000 and 2001 are a mix. It appears that many of the earlier MY2000 are dual row. If I had a 2000 or 2001, I would look at the IMS cover bolt at the first opportunity (clutch replacement, RMS leak, etc) to see what I had.

There's a good chance it's a dual row bearing. That being said, there are no hard and fast rules. My '99 has a replacement/swapped engine in it from 2000 (M96-04) and it is indeed a dual row... No longer though because I installed "The Solution" (dual row version) a little over a year ago.

If your oil was not changed annually, there could be some etching caused by stale oil. Do you have all the service history? I'd install the Solution and never give it another thought...There are many other "modes of failure" you can then focus on.

My 2000 C2 has a 03/00 build date. Whaddya think? Single/double? Btw-65k mi. TIA

My 2000 996 (production date 6/1/2000) has dual row IMS.

Looks like I am safe. Whew!

my 2000 C2 has the duel row - I think that not having a duel row bearing in an MK1 3.4 car is rare - all of the 1999, 2000 and 2001 were not included in the class action based on Porsches records that they used the duel row in all of these cars, but as many of you know there are examples of MK1 cars being torn down and revealing that they have a single row bearing. It has also been said that they changed to the single in mid year of the 2001 model but who really knows

I guess it comes down to when the engine was built, not when the chassis / power train was assembled (ie build date), as to assess if you have a double or single row bearing. Manufacturers usually have crate loads of built motors sitting on palettes waiting to be co-joined to their chassis. My old Boxster S was assembled in January 2001 but still had a double row bearing when I replaced it back in 2010, so the engine was assembled quite some time before final installation into the chassis.

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According to PCA, Jake Raby, and LN, the dual row bearing was phased out in model year 2000. If you watch any of the PCA videos with Jake, he makes a very valid point that although the dual row bearing is the most durable of the three designs, it produces twice the wear material that will contaminate the engine when it goes bad. Also, he also mentions that you can't buy any car, whether it be a 1999 or 2000 car and assume it's going to have the original dual row bearing. It's highly likely one of the owners swapped out the bearing giving you a false sense of security.

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You make an excellent point! The engine could have been assembled at a much earlier dated than the entire car was manufactured. That's probably why a small hand full of 2001 cars have shown to have the dual row bearing.

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I'm not at all sure this is accurate (my own car seems to be a violation of what's stated), but according to this post -> https://rennlist.com/forums/997-foru...ml#post7944762 996 had Double Row for engine numbers up to 661 14164 996 have Single Row from engine number 661 14165 onward Boxster: Double Row: up to 651 12851 (M96.22) Boxster: Single Row: from 651 12852 onward (M96.22) Boxster: Double Row: up to 671 11237 (M96.21) Boxster: Single Row: from 671 11238 onward (M96.21)

"996 had Double Row for engine numbers up to 661 14164 996 have Single Row from engine number 661 14165 onward Quote: Originally Posted by Stephen Tinker My old Boxster S was assembled in January 2001 but still had a double row bearing when I replaced it back in 2010, so the engine was assembled quite some time before final installation into the chassis. Boxster: Double Row: up to 651 12851 (M96.22) Boxster: Single Row: from 651 12852 onward (M96.22) Boxster: Double Row: up to 671 11237 (M96.21) Boxster: Single Row: from 671 11238 onward (M96.21)" Uh, no... It never has and never will be determined down to serial #'s... This issue has been discussed to death and no solid cutoff has been identified. The only foolproof way to determine which bearing you have b(if you've got a "transition year car" -between '00-'01) is to pull the transmission and look at the bearing flange. Dual row = Deep flange Single row = Shallow flange

^^ I totally agree with that statement dporto!

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While, as I stated, I question that data myself, an important point I think you are overlooking is that the data is based upon engine number , not car serial number. A car serial number cutoff would make no sense at all for the reasons you stated. An engine number cutoff, however, would seem to make all the sense in the world (at least on a logical level) assuming they numbered the engines in chronological order and made a hard cut switch on the engine assembly line. The reason I question the exact engine number cutoff specified is because my car does not seem to follow it. Unless they did something weird in the factory to switch back and forth between bearing types during chronological production, or to assign engine numbers in non-chronological order (both of which are possible, even though neither seems likely), it seems like there would be an engine number cutoff.

Allow me to muddy the water just a bit more. This is OPINION, has no basis in FACT, and is a supposition based entirely on logic, and puzzle pieces. There was an industrial fire in the Stuttgart production plant which affected the M96 engine line. It happened in either mid or late 2000. Engine production was moved from Stuttgart to Ulm, or NecarsUlm facility. Notwithstanding the engine SN method, I believe that all engines built in Stuttgart were dual row, as that is what the engine machine robots were designed to produce. When M96 production was setup in Ulm factory, the change to single row machining was coded into the case boring mills, and those engines were fitted with single row bearing. At some time in the future, those engines from Ulm, and remaining engines from Stuttgart which could be salvaged were mated to chassis in a rather ad-hoc way, as there was no difference in mating a single row engine or dual row engine to either a manual or tip trans car. Thus, if there were 50 engines with single row sitting there, and there were 50 2000 chassis ready for assembly, then the deed was done. If there were 50 dual row engines, and 50 2001 chassis ready, then they got a dual row(would need to be very early 2001 prod series). YMMV, don't try this at home, objects in mirror, contents have settled, and may cause **** leakage. Have a nice day.

^^^ Regardless of which theory you subscribe to (the above seems as plausible as others I've heard/read), the fact is that there is no reliable way to determine (i.e. chassis serial # or engine serial #) which bearing was used in the transition year engines short of looking at the flange or actually removing the bearing itself.

^^^ IF my theory is correct, engine SN would have to be allocated to both production lines, as there cannot be engine SN overlap. Finding the assignment of SN by engine mfg location would confirm my theory, and define the boundaries of the bearing by SN. I don't know that such an allocation scheme exists, but knowing the Germans attention to detail, I would guess that somewhere in the bowels of production records it has that type of identifying info.

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I'm not sure if this has been discussed before, but what about the engine type code? In my 2000 C2 certificate of authenticity from the factory, it specifies the engine "type" as M96/04. I think the early 1999 cars had engine type M96/01. I have no idea what the difference is between "01" and "04", but it seems like dual versus single row IMS would have been significant enough to warrant assigning a different "type" number. I'm just guessing also, but I do agree it seems very likely there is an engine number cutoff or clearly defined ranges of engine numbers that delineates single versus dual. It's impossible that Porsche doesn't have that info, but maybe they don't share it because of the lawsuit mess.

M96-01 & -02 were the earliest 3.4l (5 chain) engines. M96-03 is the 3 chain 3.6l engine. M96-04 is also a 3.4 (5 chain)engine that was built from 2000 until the M96-03 (3.6l 3 chain) began being built. See what's going on here with Porsche's numbering system? I'm sure it makes sense to them for their internal controls. That doesn't mean it makes sense to us (not in the normal sense anyway)...

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Thanks for the explanation. Definitely weird. I guess one possibility for the numbering is that they started working on the "03" 3.6 design before they decided to do whatever updates were in "04" for the 3.4 (though early 2000 would seem somewhat early to start on the 3.6). I wonder what the differences are between 01, 02, and 04. Seems weird that they wouldn't have different type for the IMS change. I guess if the 01/02/04 changes were visible externally, and the IMS change was internal only, that might explain it. I wonder what the rationale for switching to single row was to start with, at least on the 3.4. It's possible they needed a narrower space for the expansion to 3.6 (<- this is a guess, I have no idea if true), but it seems odd that they would go back and change the 3.4. The only thing I can think of is that maybe they made the change on the later 3.4's as assembly line prep for 3.6's.

Most of the decisions at that time seemed to be made by the "bean counters" with cost savings at the top of the rationale list.

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Porsche updated the shaft to a more durable, tooth type chain which ushered in the single row bearing. The 3.4L engine were known for breaking their chains, but not as much on the 3.6L because of the improved strength. Unfortunately, the horrors of the single row failures overshadowed the much improved chain system.

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Thanks, good info.

I don't know if this has been discussed before, but it seems like the Porsche IMS settlement VIN qualification criteria (cut & pasted below) would have to definitively identify which cars had single row IMS. It specifies a start year of 2001 -- that would not seem to be accurate if 2000 MY cars were affected, but maybe the VIN ranges includes 2000 models if they were affected.

That ^ is rift with errors. Here is the information from the Claim Notice http://eisenimssettlement.com/docs/notice.pdf

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Thanks for the clarification. It's a bit mind numbing to wade through the list of numbers to see if a given car is a match, but seems like this would identify all single row IMS cars (for cars that still have their original engines at least).