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Dennis Nicholls

Please verify IMS flange type (single vs. dual row)

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I bought a year 2000 986 because what I read online was that it was "sure" to have a dual row IMSB.  Well I've been disabused of this notion - there are a random amount of MY 2000 with single row IMSBs, and the only way to find out is to pull the tranny and look.  So I've done that.  Shown are two photos.  I think it's a dual row IMS flange but unlike the photo on Pelican there's no Porsche part number marked.

 

Could experienced hands please verify the type of IMS flange this is?

 

14251484248_a589f33da4_c.jpg

 

14251484008_8aa551ba15_c.jpg

Edited by Dennis Nicholls

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Yes I've done that but I'm looking for verification.  The ones posted on Pelican's site have part #s stamped onto them.  Mine is plain.   Looks like a dual row to me.

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I bought a year 2000 986 because what I read online was that it was "sure" to have a dual row IMSB.  Well I've been disabused of this notion - there are a random amount of MY 2000 with single row IMSBs, and the only way to find out is to pull the tranny and look.  So I've done that.  Shown are two photos.  I think it's a dual row IMS flange but unlike the photo on Pelican there's no Porsche part number marked.

 

Could experienced hands please verify the type of IMS flange this is?

 

14251484248_a589f33da4_c.jpg

 

14251484008_8aa551ba15_c.jpg

 

Looks like a dual row to me.  LN used to have a photo comparison of the flanges on their website for comparison purposes, you might want to look that up just for your own peace of mind.

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I went over and took a look at the LN websites....I didn't find any comparison photos.  IIRC they have "pruned" their website recently.

 

My problem is that I'm now at the stage of ordering an LN kit and if I order the wrong one it's not exchangeable.  I'm just being careful.  My engine serial # is 2265Y13700, and just the "Y" alone means it's most likely a dual row IMSB. 

 

Also....this is a fish-or-cut-bait moment.  If I'd found a single row IMSB, the probability of failure P1 = 8% to 10% is unacceptable to me.  But a dual row probability of failure P2 = 0.7% is much lower.  There's a third probability P3 that I will screw up the installation.  If P2 < P3 < P1, then I may be tempted to just change the RMS and clutch and call it a day.  If P3 < P2 then I should proceed to change the IMSB.  And for me P3 is unknown.

 

I've followed with interest reports on this and other forums of dual row IMSB failures.  They appear from this small sample size to be mostly a problem with the 3.2l "S" engine, not my base 2.7l engine.  Even Jake Raby (in an unguarded moment I'm sure) made a comment that he seldom sees any problems with the 2.7l engine.

 

What I found at 53K miles is a non-leaking RMS and IMS flange seal.  I measured the thickness of my new vs. original clutch disc.

 

New clutch disc 0.356 inches.

Original clutch disc 0 346 inches

 

I may be forgiven if I feel I've been "suckered" into pulling the tranny and flywheel on a wild goose chase.

Edited by Dennis Nicholls

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Should you go on and change it? Depends on what you'll do with the car in the years ahead and how do you know that for sure.  I've invested $$ only to have to total the car 4 months later. Or put new Michelins on only to sell the car with maybe 3-400 miles on the tires. OTOH, you are half way there....

 

Got access to the tools? Or is that a cost too?

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I pre-purchased the LN tools and all the misc. small parts, e.g. chain tensioner metal seals and O rings, and the cam end green plastic plugs.  I could easily re-sell the tool kit whether or not I use it.  It makes sense to pull the tensioners (one at a time), clean them with fresh oil, and reinstall them.

 

OTOH if I end up selling the car, having an LN IMS bearing installed, with paperwork to prove it, should be a great selling point.

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I went over and took a look at the LN websites....I didn't find any comparison photos.  IIRC they have "pruned" their website recently.

 

My problem is that I'm now at the stage of ordering an LN kit and if I order the wrong one it's not exchangeable.  I'm just being careful.  My engine serial # is 2265Y13700, and just the "Y" alone means it's most likely a dual row IMSB. 

 

Also....this is a fish-or-cut-bait moment.  If I'd found a single row IMSB, the probability of failure P1 = 8% to 10% is unacceptable to me.  But a dual row probability of failure P2 = 0.7% is much lower.  There's a third probability P3 that I will screw up the installation.  If P2 < P3 < P1, then I may be tempted to just change the RMS and clutch and call it a day.  If P3 < P2 then I should proceed to change the IMSB.  And for me P3 is unknown.

 

I've followed with interest reports on this and other forums of dual row IMSB failures.  They appear from this small sample size to be mostly a problem with the 3.2l "S" engine, not my base 2.7l engine.  Even Jake Raby (in an unguarded moment I'm sure) made a comment that he seldom sees any problems with the 2.7l engine.

 

What I found at 53K miles is a non-leaking RMS and IMS flange seal.  I measured the thickness of my new vs. original clutch disc.

 

New clutch disc 0.356 inches.

Original clutch disc 0 346 inches

 

I may be forgiven if I feel I've been "suckered" into pulling the tranny and flywheel on a wild goose chase.

 

ims-later-single-bearing.jpg  ims-early-double-bearing.jpg

 

          Single row                                                     Dual row

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My dumb questions. Can't you just take the darn thing out and see?   Can you stand the down time while the verified part gets shipped?

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Mike,

 

Two reasons.

 

One.  I was considering not changing the IMSB if it were a dual row bearing.  You can't put a bearing back in once you've pulled it, since the puller stresses the inner race.

 

Two.  I don't like leaving the engine open for a week or two until I get the new IMSB installed.  Too many dust storms etc. around Boise.  I want to pull the original bearing only when I've got the new bearing sitting in the freezer ready to be installed.

 

LN bearing on order today from the cheapest place I found, OEMBimmerparts.com for $577 shipped.

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I was thinking of covering the IMS shaft with a bit of plastic and tape wile waiting.

 

Good luck. Your research tells me you'll do well.

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Kudos to OEMbimmerparts.com . I ordered online Tuesday AM, and they shipped free UPS ground from Portland, OR.  It arrived this morning.

 

First time I've seen an IMS bearing in the flesh.  Geez this thing is tiny.  How did Porsche pick such a tiny size bearing to support the business end of the IMS?

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You'll be glad you replaced it; mine crapped out at 58,000 miles. It's a dual-row, 2000 S. If it goes out completely and trashes the motor, your car is basically a boat anchor at that point.

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Dennis , Thanks for raising this issue of identifying which bearing/flange is present for the problematic 2000/2001 period. I have a 2001 Boxster S and am doing a total rebuild but still had problems identifying the parts.I offer a small addition to your good work below.

There is some half helpful info on the parts sites that mentions a "cover dish" depth of either 13mm or 19mm for 2row/1 row. But they do not give any reference to where to measure the distance exactly ! Saying "deep" or "very deep" dish doesn't help either unless you have a known example of each ! The situation is further complicated by after-market parts and the fact there is a no-returns-accepted disclaimer on parts that won't fit /mistakenly ordered.Why?

If you look carefully at the helpful Pelican photo linked above ,you'll see that the flanges of the OEM deep dish/single row has a unique buttress that extends the inner edge of the flange into the center of the cover.That may be a useful clue if you have an OEM flange ?

IF you have an LN cover dish marked "E3"  ,it seems to be different.

I have a singlerow LN hybrid ceramic bearing with the LN cover - purchased as a kit from Pelican #106 08 2 .But the cover dimension seems to be for a doublerow ! .This cover is only 13mm deep(=shallow =2 row) from the outer face of the flange(where the 3 flange bolts fit) to the deepest part of the dish(where the center stud nut fits). I'll try to upload some photos later to show where I measured.

My suggestion is to send a vendor photos similar to mine and let them decide which you have because they will have the deep/shallow parts to compare and could at least give some specific dimensions.

Edited by Schnell Gelb

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Dennis , Thanks for raising this issue of identifying which bearing/flange is present for the problematic 2000/2001 period. I have a 2001 Boxster S and am doing a total rebuild but still had problems identifying the parts.I offer a small addition to your good work below.

There is some half helpful info on the parts sites that mentions a "cover dish" depth of either 13mm or 19mm for 2row/1 row. But they do not give any reference to where to measure the distance exactly ! Saying "deep" or "very deep" dish doesn't help either unless you have a known example of each ! The situation is further complicated by after-market parts and the fact there is a no-returns-accepted disclaimer on parts that won't fit /mistakenly ordered.Why?

If you look carefully at the helpful Pelican photo linked above ,you'll see that the flanges of the OEM deep dish/single row has a unique buttress that extends the inner edge of the flange into the center of the cover.That may be a useful clue if you have an OEM flange ?

IF you have an LN cover dish marked "E3"  ,it seems to be different.

I have a singlerow LN hybrid ceramic bearing with the LN cover - purchased as a kit from Pelican #106 08 2 .But the cover dimension seems to be for a doublerow ! .This cover is only 13mm deep(=shallow =2 row) from the outer face of the flange(where the 3 flange bolts fit) to the deepest part of the dish(where the center stud nut fits). I'll try to upload some photos later to show where I measured.

My suggestion is to send a vendor photos similar to mine and let them decide which you have because they will have the deep/shallow parts to compare and could at least give some specific dimensions.

 

If you look at the photos I posted in post #11 above, the factory single and dual row flange covers are entirely different and very easy to visually discern; the dual row flange is nearly flat in the center while the single row flange is deep with sloping sides.  We have never had to measure one, just a quick peek tells you what you are dealing with.

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Yes, it is the buttress that is the easy to spot distinguishing feature but I never saw that feature mentioned so thought it helpful to point is out.

If you have an LN cover plate the photos above will give the wrong and very expensive identification as explained above. I can't get the photos resized yet but will try later .Hopefully that will clarify.

Meanwhile I found some engine number references that may be (??) helpful.Others feel free to correct.

 

Double row = M96.21 651 12851 - 671 11237. Mine is 671 11708 but has a single row dimension LN cover.LN 106-08-2

 

Single row =651 12852/ M96.22 -67111238/ M96.21

Edited by Schnell Gelb

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Yes, it is the buttress that is the easy to spot distinguishing feature but I never saw that feature mentioned so thought it helpful to point is out.

If you have an LN cover plate the photos above will give the wrong and very expensive identification as explained above. I can't get the photos resized yet but will try later .Hopefully that will clarify.

 

I hope it will as I do not really see your point.

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Dennis and I are both Engineers. Neither of us could figure this out quickly. There are lots of posts elsewhere asking the same question: "which bearing do I have?"- particularly for the cross-over years of 2000/2001. In no other post I could find  mention of " buttress". It is an obvious i.d. point for those of us who don't have your experience nor the two different parts to physically compare. .So it is easy to i.d. the two bearings ?

Perhaps not.

Even engine numbers may be an unreliable predictor of which bearing is present. Perhaps a replacement engine?  Or an after-market bearing+ cover plate?

My engine number indicates it should be fitted with a double row bearing. The LN cover plate I have just removed from this engine measures as a double row bearing should. But if I ordered a double row replacement, it would not fit .Why? The LN bearing currently fitted is a singlerow.It came as a kit form Pelican -LN106-08-2 mentioned above.The cover plate in this kit measures as a doublerow,not a single row. It has no buttress and looks exactly like the double row bearing cover plate in the Pelican photos.This LN bearing is marked 6204RS1/1 on the single seal &  "LN Engineering" on the outer race, with 8 ceramic balls.The bearing removed to fit the LN part was a single row OEM Porsche part that I still have .It is marked NSK 6204-DU17.

If one of our readers orders the wrong part, it is a $600 mistake. Just thought this word of caution and a few photos may be helpful ?

I'll try and unravel this mystery and post the photos later to help others with the same issue.

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Dennis and I are both Engineers. Neither of us could figure this out quickly. There are lots of posts elsewhere asking the same question: "which bearing do I have?"- particularly for the cross-over years of 2000/2001. In no other post I could find  mention of " buttress". It is an obvious i.d. point for those of us who don't have your experience nor the two different parts to physically compare. .So it is easy to i.d. the two bearings ?

Perhaps not.

Even engine numbers may be an unreliable predictor of which bearing is present. Perhaps a replacement engine?  Or an after-market bearing+ cover plate?

My engine number indicates it should be fitted with a double row bearing. The LN cover plate I have just removed from this engine measures as a double row bearing should. But if I ordered a double row replacement, it would not fit .Why? The LN bearing currently fitted is a singlerow.It came as a kit form Pelican -LN106-08-2 mentioned above.The cover plate in this kit measures as a doublerow,not a single row. It has no buttress and looks exactly like the double row bearing cover plate in the Pelican photos.This LN bearing is marked 6204RS1/1 on the single seal &  "LN Engineering" on the outer race, with 8 ceramic balls.The bearing removed to fit the LN part was a single row OEM Porsche part that I still have .It is marked NSK 6204-DU17.

If one of our readers orders the wrong part, it is a $600 mistake. Just thought this word of caution and a few photos may be helpful ?

I'll try and unravel this mystery and post the photos later to help others with the same issue.

 

Which is why you should always pull the existing bearing out if you have any questions about which style it is.

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