AT in engine number
 

I am trying to confirm that "AT" in the engine number means that it is rebuilt? Does anyone have some solid facts on this? The engine number and VIN do not seem to match on the car. I am not overly concerned and in fact would rather that it was a rebuilt engine so I don't have to worry about the IMS bearing. Anyone have any solid information on this? Many thanks!

I've had two 'AT' engines. My understanding is that it is either new or remanufactured as a replacement engine by Porsche. It does not imply anything about the IMS bearing, but I think that the larger unserviceable bearings are more common in these engines.

It's not "rebuilt". AT means "Austauschmotor" and is an exchange engine originally from Porsche. We don't know exactly what its life story is.

It is a factory reman engine that matches what was originally in the car.

Yes, it is a rebuilt or remanufactured engine.

Thanks
 

Thank you all for confirming the answer to my Boxster engine question (has AT in the serial number). Very helpful!

It doesn't always match what was originally in the car. I have a 2002 with an "AT" engine. If I'm not mistaken, that model year came with a single-row IMS bearing. I planned on changing it while the transmission was out for service and the IMS tool I bought from LN wouldn't even fit the bolt. It turns out I have the engine with the upgraded LARGER single-row IMSB. LN wouldn't take the new, unused tool back. As you might guess, I'm still not happy with them.

The engine was a match for what was in the car, including ALL UPDATED PARTS SINCE THE CAR WAS FIRST ASSEMBLED, which is pretty much the way they have always done things. After getting stung with a class action over the single row bearings, they switched the the oversized non serviceable unit, which was an updated part. Any other updated parts were also replaced, but otherwise the AT engine was a match for the original one.

Sorry, I don't mean to split hairs with you but an engine with "updated parts" is not "an engine that matches what the car originally came with." I would imagine that the engine block's casting or milling has to be different in order for the oversized bearing to fit. So, no, it doesn't match what the car came with.

I only mentioned it so if the OP someday decides to service the IMSB they will know NOT to rely on what the car originally came with, as I did.

The OEM's are required by law to include ALL updates in reman engines, particularly if the replacement is a waranty issue, and/or if there is a liability issue involving the update components; so with the exception of the updates, it otherwise replicates the original engine. The object is to keep the warranty recepient "whole", and prevent any known possible failure issues.

As for which AT engines carry the oversized IMS bearing, the AT serial number can be decoded to determine its date of remanufacture; so AT's prior to PCNA switching to the oversized bearings would contain exactly what bearing the original engine carried; those producted after the change over date would carry the larger bearing. And just to address your point of contention, the engine cases carrying carrying the oversized bearing are EXACTLY the same as the original, only the IMS shaft was changed to allow the use of the large IMS bearing.

Early and late IMS shafts:

https://lnengineering.com/media/cata...106-08.1.l.jpg

You want to keep splitting hairs. I never disputed that they use updates and I don't want to argue with you.

I just wanted to clarify that if a car has AT engine, it's not necessarily the same as the engine that originally came in the car. It may FUNCTION the same, it may work with the cars' electronics the same way, but it's not necessarily the same as the original. That's useful information to for people know, especially if they plan on doing the IMSB, that's all.

Yes, and that makes it different than what was in the car originally. It's important that people know that instead of telling them they have the same thing. I spent a lot of time and money thinking I had a 2002 engine with a 2002 IMS bearing. I don't want others to go through what happened to me.

Not to be pedantic, if the serial number for your AT engine showed assembly before 2004, it would have had a single row, serviceable IMS bearing; if the date were 2004 or later, it would be carrying the oversized bearing. If the date of assembly came back as late 2003, standard retrofit practice would be to look and see which bearing is in the shaft before ordering parts, just to be safe and not waste time and money as there was definitely some overlap during the changeover.

We do this for a living, so we have seen most, if not all, ways one of these retrofits can go sideways and try to avoid those pitfalls.

So you already knew they're not always the same.

I didn't have the luxury to see which bearing was in the car. I had a really short window of opportunity when the transmission was out for the rebuild, so I had to order everything in advance before taking the car to the shop. Thankfully, Pelican Parts graciously took the bearing back. I can't say the same for LN and the tool I couldn't use.

I just wanted the OP and others to know, in the event they decide to service the IMSB. Peace. :cool:

No, the engines ARE the same, only the IMS shaft has been changed to the updated version. But if it makes you feel better, be my guest.....................

They're the same but depending the build date, you can or cannot service the IMSB. Ooooookay. :rolleyes:

You can tell them what you want. I just wanted them to know that, if they intend on replacing the IMSB, they MAY NOT have same type that originally came with the car. And, if they've been following, I'm sure they understood.

Which is why it would be THEIR responsibility to find out what they are dealing with before they order parts they may or may not be able to return.............

....because it's not always the same. If it was the same that came with the car they wouldn't need to, would they? Just sayin'.

Look, ALL the necessary information about which type of IMS could be in the engine is readlly available to ANYONE that takes to time to look and do some reading. If one choses not to do that, mistakes can be made, but not because this is some kind of mystery, it was by choice........