Clutch repair in process - two questions

I've got the transmission out of a 99 AS with 95k miles - started to slip in gears 3, 4 & 5. Good thing, there's no meat left on the bones.

Since I'm in there already, I'm thinking of the IMS bearing replacement; any comments? I am thinking of the LN Engineering ceramic bearing.

Also the transmission shaft main bearing (behind the support tube in the bell housing) does not have a full complement of ball bearings - it only has about half the bottom circumference of the circular bearing. Does that sound right?

Since it's all apart now's the time - any input would be appreciated.

Phil

I cant comment on the tranny bearing, sorry.

I think, if you are in there, do the IMS. You have two choices - get the factory one, or get LN. The LN one is very over-built, and therefore should be permanent. Of course, your last factory one went 95k miles too. But i'd do the LN.

Now, you'll need to removeal tool (puller); and a cam lock set, and a pin to hold the flywheel, and lots of guts before the glory, if you've never done one. Also get new plugs for the cam tensioner access.

I dont know if you can rent to cam-locking tools.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Thanks for the input, I'm going to do the LN IMS, as I want to keep the car for another 100k miles. Pelican has a tech writeup on how to do it, which I'll follow. LN also sells a bearing puller kit as well.

I'm less worried about the IMS than about the main shaft bearing on the front of the transmission - who would be a good resource to ask?

Thanks for the responses.

Phil

And pretty robust - moreso than the 6-speed units.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

I tend to if it ain't broke don't fix it but the trouble is while IMSB may not be broke it goes from ok to broke in very little time.

It depends upon how in touch you are with your car. If you hear a disturbing noise would you shut off the engine first and ask questions later?

If so then at this time, if this time ever comes, you could do an IMS bearing upgrade I guess.

As for the transmission bearing question... I can't imagine a scenario in which a healthy bearing could have any balls/rollers missing.

The bearing must have its full complement of balls/rollers and they must be properly spaced -- held that way by the bearing retainer.

If you are indeed seeing what you report -- high res pics would be nice -- I'd have to say that transmission is sick.

But before you tear into it get a 2nd opinion. Have another more experienced pair of eyes give it a looking over to be sure what you are reporting is correct and that there is not some goofy bearing that functions short a few balls/rollers.

Sincerely,

MarcW.

My indy is an ex-Porsche shop foreman and has his own shop now. He does the replacement and is neutral on advising for/against it. He has done quite a few now and he has pulled out a few that were failing.... no noise or symptoms, but clearly failing. These engines were clearly saved. He also pulled out many more that appeared perfect. So should you do it? I dunno.

Given my value system of keeping cars a long long time, I think I will probably do it when my clutch goes.... if it goes. I have 194K miles on my original clutch..... who knows when that will go as I always rev-match. Even the Porsche mechanic tells me it is like buying life insurance. Do you really need it? Only you can answer that. He has said, going way back, that he has never seen engine failures to the high degree from these engines.... I don't want to open the debate as to "how frequent" etc. but he said that when you compare the engine failure frequency of these engines with past Porsche engines, there is no comparison and he was shocked at what he feels is just cheaped-down engines. He said the fundamental reason for these failures is that Porsche just cheapened them.

When I was in Altanta, having my failed engine replaced at 47K miles (2000 S), there was a poster at Don Ellis Porsche there in the service lounge that read something like "All Porsche parts are race tested". No more.

Oh, they were working on one of the engines they saved and showed me the bearing... awful looking. He said, and showed me the intermediate shaft... they saved the shaft by doing some machining to the end where the bearing was failing and was grinding it up. Fortunately, the pieces had not entered the engine. They told me the price of the shaft... don't remember but it was expensive. Apparently this one made noise.

Even seeing this carnage and hearing the stories first hand, I still won't do it unless I have the clutch replaced. Again, the mechanic was neutral about it as there are still a heck of a lot of engines still humming away nicely.

Agree that if you already have the tranny out for something else, the LN bearing is worth doing. Probably also worth doing the RMS if it has a few years on it. I choose not to worry about it until clutch time and given my history, that could be awhile (2001 S, just crossed 70K). It's all about individual risk tolerance, as innumerable previous threads have addressed.

I wouldn't use the Pelican method for replacing the IMSB. Use the LN eng. method. Engine pinned at TDC, lock out both cams and remove all 3 chain tensioners.

I was confused by the pelican method. So i read it about 20 times and concluded he was in fact making a home-brew locking contraption and in effect jamming the motor in position. Unfortunately he never says so. Its one of the many, many omissions in that book. Clever idea, terribly written

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

I looked at it Friday and it is well done...not step by step but certainly hits the important stuff.

dghii
2000 Boxster S 6speed 112k miles