Roy, what mileage did you have your transmissions replaced at? Did you do much track/DE?

 

Another way of looking at it:

- Let's assume, as posted before, that the engine will break between 100k and 200k miles, for sure.
- Now, let's assume that your engine pops at 33k miles. In this case, you are spending what, 15k in a LN engine if you want to be "safe", right? And, that engine will last you for.....? more than 200k? doubtful, and for sure unproven.

So, instead of preventing it, let your engine run its course and not spending $15k in preventive measures, which is how much an LN engine is due to have to change the cylinder sleeves for NicKies among other things. See how long your original engine lasts, and then spend the money when it pops without obsessing about it. If you keep the car long enough, yes you would spend the money to 'buy yourself" another 100k as part of cost of ownership.

IMS upgrades make sense because it is very inexpensive by comparison.

 

996 GT3 and TT models didn't exhibit the IMS issues like the others. 997.2 NA models is when the IMS isn't an issue. 997.1 NA still had IMS issues. Either way, if you have to worry about it this much to affect having fun with it, this isn't the car for you.

 

Contrary to what RugRunner said all TT's until the 9A1 engines came out in 2009 had IMS shafts. However the design of the engine in the TT's was completely different than the 996 non-turbo. The TT's were derived from the old air-cooled engines and the IMS was completely different in design and had pressure fed bearings.

 

I know just enough to get in trouble...or make a clown of myself. Dharn55 is the voice of technical wisdom coming from above, helping guys like me learn. Thanks, Dharn!!

kyle

 

Why delay enjoying the extra 40+ ft.lbs. torque from the big bore LN sleeves? Do the "preventative" upgrades now & it may go 200k miles & the extra Smiles are guaranteed!

 

Are all the 2001 engines better off than the 99 or 00's? Or are there certain in service dates that they beefed up the IMS? Thanks.

 

Actually Porsche "downgraded" the IMS bearing somewhere between 2000 and 2001. The original IMS bearing was dual row and has a higher load rating than later cars. Porsche went to a single row bearing in or around 2001 to 2002. Sometime during 2005 they went to a much larger unservicable (without engine tear down) bearing, with similar load capabilities to the original dual row bearing.

Of course, a retrofit bearing from LNE remains to be the highest load rated bearing the consumer can purchase.

So in some respects, the early 996's in 1999-2001 range are "beefier" than the later model year cars.

Here is the best read on the subject:

http://www.lnengineering.com/ims.html

 

There is someone in Spain that has replaced the bearing with a ceramic / hybrid helicopter bearing that allows oil to flow through and thus guarantees lubrication. Look under 996 forum . The title of the thread is "The ultimate IMS Upgrade" .

And here is the website that talks about this upgrade.

http://www.insaroims.com/pedidos.php

 

I've read on here that you can decode your VIN numbers to make apparent any issues with the IMS? Is this truly possible? It seems a little far fetched but I am incredibly nervous about my '99 with 60k developing these issues.

 

At 106,000 Miles my engine went (cracked heads). Done a total engine rebuild with new heads. Ton of other mods already done to the car and engine.

 

I have a 99 with 145k and never had an issue. It seems to be luck of the draw. Enjoy the car.

 

Sorry but I have heard just the opposite - the the early 3.4's had the double row bearing which was better - I have also heard (lately) that higher miles is better - I guess the idea being that at 70k on the clock if the bearing was going to be problem it would have already done so.

 

No, I have not heard by VIN - but I have heard that you can by engine number - that's just what people say - bc the want to feel better - there is no way to know - single race - double race 3.4 or 3.6 - doesn't matter - my formula is "nothing w and S" and s tells me that someone wants to race it - but I am the only person that drives their c4 like one of the little german autobahn ladies.

 

While I agree that the evidence suggests that the dual row IMS bearing was more robust than the single row replacement, this is an easy to replace component. There were other changes to the 3.6, such as modifications to composition of the alloys used in the cylinder sleeves (reduce D-chunk failures) and a beefier crankshaft.

All in all I would welcome a real analysis on which rev is more reliable, but I doubt Porsche will be forthcoming with the data.