1999 996 with AT crated Engine - IMS Help Needed

I have as stated a 1999 996 but in 2008, Porsche dealership installed a crated (per service invoice) engine. The Serial number on the engine is M96/01AT66X67411. My question is this, is this a 1999 replacement engine that was installed in 2008? If so, would this have the M97 IMS non-serviceable Bearing or would it have the 1999 Double Row IMS Bearing? Is there a way to tell without removing the transmission? The engine has 42k miles on it and I am wondering if I should replace (if possible) the IMS Bearing. Much appreciation for the help!

I believe you need to get eyes on it to be certain. I have an AT motor in my 996.2, so I read everything I could find. From everything I read, the AT (austauschmotor) coded remanufactured engines from this timeframe have all of the running updates including the new large IMS bearing and associated shaft. But the only way to be certain is to get eyes on it. If the nut on the flange is the large nut, it is the large bearing. You can be positive if you remove the flange and observe/measure the OD of the bearing. If it is the large bearing it will have an OD larger than the hole, so removal and replacement will require splitting the cases. LN told me these are reliable bearings and they only recommend removing the outer grease seal on the bearing to allow oil to lubricate the bearing.

Thanks for the reply, this is great info. So for the dumb question, do you need to drop the transmission to inspect the flange and nut? I would assume so.

Your assumption is correct.

M96/01 originally had the dual row bearings in them... Not sure if they changed to larger bearing when "re-manufacturing" these engines.

I agree with both of the above posters. Yes, you have to pull off the transmission (and remove the clutch flywheel) to be sure. As an aside, I've wondered if you could mill an access hole and see (right where the IMS Solution oil feed would go in the flange), but I wouldn't dare to do it to my engine as the first test... On the engine, your guess is as good as ours. We don't have anybody that really knows, so we have to base our answer on repeated assertions, anecdote and internet "facts". Your car most likely originally came with a dual row bearing. Everything I've read about Porsche AT engines is that they get the running changes - information is scarce though. If I were a betting man, I'd bet your engine has the large bearing. The only way to know for certain is through direct observation. Not to beat a dead horse, but if it is the late large single row bearing, it can't be removed with the engine in the car. It requires engine removal, strip down, and splitting of the cases to get to it. It would be uneconomical to do this on an otherwise healthy low mileage engine.

Quotes source post: 16056904

Depends on when the engine was built, but I would make the assumption that it has the larger 06-08 non-serviceable bearing. Regardless, it's a good idea to go in there to be 100% sure as there is a remote possibility if that engine had been on a shelf for a few years that it could have the smaller single row bearing, as the engines received whatever was the current bearing at time of manufacture.

Might as well get in there and change the RMS and AOS. I too have an AT for my .2.

Another AT engine guy here. Serial M96/01AT66X67127, which is prior to yours. The previous owner dropped the transmission intending to changing the IMSB and found the later, large bearing. He ended up removing the seal (and replacing the RMS and clutch). He gave me a picture of the larger bearing so I'm trusting that it has the larger bearing. My guess is you have the large bearing too. However, you won't know for certain without putting eyes on it.

You want to get eyes on it anyway so you can pull the seal off. Mine had 50K mile and lots of oil in the bearing (not good long term)

My car is an 02 but same as yours Porsche replaced the engine in 08. While changing the clutch I confirmed it has the larger 06-08 non-serviceable bearing. All I did was removed the outer bearing seal and called it a day.

Thank you for all the replies. To be safe I will take it in, pull the transmission and visually verify what�s in there. I�m not a betting man but given the replies from you guys there is a good possibility it�s the larger bearing. Not sure if that is good or not. I preferably would like to put a ceramic bearing in there while everything is opened up but it seems the failure rate on the larger Bearing is very low. I�m not sure I like the idea of pulling the seal but it makes sense to let oil in to keep it lubed. Thanks guys.

I'd wait till you need to replace clutch or any other thing that requires an engine drop. Just monitor your oil (oil analysis) and check your oil filter at each change every 3-4K miles.