996 IMS, timing chain guide, transmission pinion bearing and misc items DIY project

After reaching 100K miles on my 99 C4 daily driver I decided it was time to do some maintenance to keep her on the road for another 100k. My list consist of the IMS bearing update, RMS seal, replace all the plastic timing chain guide (as I have been finding plastic debris in the oil filter), air oil separator, and replace the pinion bearing in the transmission. So Chris Walrod and I attached this job together, with Chris's transmission expertise he was a great help in getting the transmission apart and was able to replace the pinion bearing which required the removal of all the gears. Porsche went cheap on the 996 transmission, instead of using a splined shaft, they went with an interference fitted gears. Which means the gears will require a press with some force to get them off. Unfortunately to replace the pinion bearing you will have to press all the gears off in order to get to the bearing. Besides the IMS bearing being a sealed bearing Porsche also used a sealed bearing for the pinion bearing in the transmission. So it is was just a matter of time before all the grease leaked out of the sealed bearing and the bearing eventually will burn itself out. Most people probably will not notice that their pinion bearing is bad unless you know exactly what to listen for. Basically in my case I heard a dragging whoooshing sound whenever the car was moving, almost sounded like wheel bearing. The noise was regional to the transmission area, so we knew for sure it was the pinion bearing. Here are some pictures of the work performed. Engine comes out much easier than a 993, there are really only 4 bolts that holds the entire engine and transmission on the car. The hardest part of the engine removal is the removal of the A/C compressor and getting all the coolant pipes off. I decided to keep using the clutch, pressure plate and flywheel as they were still in good shape at 100k miles. The midrise scissor lift offered plenty of room for the engine and transmission drop and have room to store the engine underneath while it was being worked on and still allowed the Italian mistress to park inside the garage. Here is the new air oil separator In order to replace some of the plastic timing chain guides you will need remove the cam shafts. Of course make sure the car is locked in TDC with the pulley pin, and you will need to have all the proper cam shaft tools to lock the cam shaft and to hold them in place and the compressing tool to compress the vario cam solenoid. Good old chop sticks method to make sure TDC on cylinder #1 The cam drive spracket will also need to be removed in order to remove the cams. Here are the cam shafts Lifters Here is one of the main chain guide, there were some wear but not as bad as I thought. These are the guides for the cam shaft chain, they were in really bad shape. Do the same thing for cylinder 4-6, don't forget to turn the crank shaft so it is now locked TDC on cylinder 4? Can't remember, read the shop manual. In order to replace the main chain guide on cylinder 4-6 you will need to remove the oil pump and the entire oil/coolant manifold assembly. While I was at it I replaced the thermostat, the water pump was still good since it was replaced at 60k miles. This is the hex drive that drives the oil pump Extraction tool to remove the IMS bearing New IMS bearing installed. The kit was very nice from LN engineering, I am definitely a satisfied customer. This is the old IMS bearing, all the grease was washed out of the bearing. It was matter of time before it gives out. Another while I am at it item, the RMS. The old one was not leaking, but why not. I did use the special RMS installation tool to make sure it was pressed in at the proper depth. Nose cone off on the transmission It helps to have the transmission on a engine stand to work on Shift forks removed Gear cluster removed from the main case This is how badly the pinion bearing was pitted, which explains the scratchy noise I was hearing Pitted spider gear, another common 996 transmission failure area. New pinion bearing pressed back in, we decided to leave the seal off to allow the bearing to receive splash lubrication from the gear oil. No one really know if this would prolong the life of the pinion bearing, but I guess we will find out. Since now we know how to rebuild these they are not so bad. At 100k miles my gears, synchros were in almost perfect condition. I expected this as I never abused my transmission by doing anything stupid. Heating up the main tranny case to install the gear clusters Cluster back in The mating plate requires a special torx tool Shift forks installed I did upgrade the clutch fork pivot kit, cleaning the spline and upgrading the clutch fork and throw out bearing made a day and night difference on how smoothly the transmission shifts now. All back in and runs like a champ!

That. Is. Amazing! You actually managed to make it look like a 360 spyder!!!

The 360 spider only dream to be as reliable as a Porsche. :P

well done - GREAT PICS !!!

Hey Robin, great write-up and pics! Thanks for sharing.

wow thats very impressive DIY, Kudos to you!! How many hours?

Thanks guys, I lost count of the hours. I would say the cleaning and scrubbing took most of the time. The 996 is a lot easier to work on than the 993, so much more space in a very nicely engineered package. I guess when Porsche did it from scratch with the 996 they learn from all of their previous mistakes with air cool cars and applied it on the 996 design. I was very impressed with the overall 996 mechanicals after this little exercise, just wish they would not have used sealed bearings.

Very nice!! Coming down to New Zealand anytime soon?

Nice pics and write-ups, do you have a DIY for dropping the engine out???

can i drive to you and have you do that to... i'll pay of course... : )

Thanks for posting. So did the plastic found in the oil filter match that of the ramps? I haven't found any in mine. Sealed bearings argh. Regards,

The procedure outlined in the shop manual for dropping the engine is pretty detailed and simple to follow. Only tips I can offer to ease the process is to use a plastic pry tool (made for removing interior trim pieces) to pry all the rubber coolant hose, spray a little brake parts cleaner into between the rubber hose and the metal piece and work it out slowly. As for the AC compressor removal I found that if you remove the throttle body you can reach your hand in to help guide the socket to get to that angled bolt. The plastics found in the oil filter was indeed the same plastic (color) as the ramps. Mike, if you drive out here I would be glad to work on it for you.

Robin! You are the man!!!!!!!! Excellent writeup and I must say takes some of the fear factor out of DIY (some but not all for me, i need to find a bit more courage but I am getting there with articles like yours!) Pete

Great pictures and write up! Now you're ready for 100k more miles.

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That's the plan! I love to use my 996 as a daily driver, one of the most reliable and economical car I've ever owned.

Nick, I talk to a lot of people all the time about our Porsches so I apologize your name doesn't ring a bell right now. But I could be having a senior moment. Most everyone knows me on the 993 board, due to all the DIY projects on the 993s I posted on my web site http://p-car.com which are the same DIYs listed on Pelicanparts.com Chris Walrod and I work on bigger 993s projects often on weekends, more for fun than anything else as we both have regular day jobs. We have no intention of opening a shop, just want to keep things on a fun level. I haven't had the need to create the same DIY site for the 996 because there isn't much you need to do with these cars. I lived in Atlanta for 7 years and then 2 years in Miami, moved back to Southern California in 2004, not sure if I am the same Robin you were referring to.

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Note that I am not disputing the wisdom of replacing it (I would have done likewise) but aside from it being devoid of grease (presumably it had been lubricated by oil splash, just as the new LN bearing will be) what do you base your conclusion that it was going to give out? Was there slop in the bolt shaft, play in the bearing itself, pitting of the *****, damage to the ball separator, etc.? An article in Total 911 states the opinion of some Brit authorities that if the bearing survives long enough for the seal to give way so the bearing gets freely lubricated from cam chain oil splash, it will likely last the life of the engine. I'm just curious what physical condition your IMS bearing was in after 100K.

The Pinion bearing in my daily driver 996 is also on the way out. It's been whining for some time. I have a friend who can do all of that stuff - other than pressing the bearings off and onto the tapered shaft. I understand that a really high load press is needed for that job. How were you guys able to get that done? I'm curious because I may ask for your help with this job, at least in that area. Great job and thanks for the writeup and pictures!

Thank You, Thank You, Great Pictures,WOW!

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There are two problems with the splash lubrication theory. (1). There isn't enough splash, I noticed the oil that came out were dirtier than the rest of the oil, which tells me that there isn't enough circulation in that area (2). The seal cover prevents enough of the splash to get into the bearings to keeps them properly lubricated. I will be sending my bearings out for testing and to see exactly what condition they were in.

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The hardest part was to press the gears and bearing off, which required a very high tonnage press. In addition you will need to fabricate plates of various size to grab on to each of the gears while they are pressed out. You should contact Chris Walrod for details, as he did all the pressing and fitting. Thanks

great write up!! thank u

Many thanks for sharing, great pictures too. Can we have that sticky somewhere so my dumb head cant lose it?.

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So basically what you're saying is that LN Engineering, who designed and sells the retrofit bearing which depends entirely on splash lubrication, is wrong on their basic premise. So why then did you put in a bearing requiring splash lubrication rather than re-pack the original one with grease and put in a new seal?

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Because the bearings used by LN's will last 3 times longer even with moderate splash lubrication. They even say that on their web site: "ur kits replace the factory sealed bearing with a new, severe duty custom ceramic hybrid roller ball bearing for reduced friction and superior performance in poorly lubricated operating conditions and replaces the factory IMS flange hub, bearing support, and fastener with a stronger, revised billet chromoly assembly."

This is the main issue with sealed bearing in the engine and gbx, the grease slings out presumably from centrifugal forces / heat and oil cannot get back into the bearings to offer proper lubrication. If you pull the drain plug on the trans, you can reach up there with your pinky (sounds nice, doesnt it) and feel for excessive lumps of grease on the magnet located about an inch from the drain plug port. If you feel the grease, its come from the pinion and or layshaft bearings. Just a matter of time at that point

Very nice guys I appreciate the photos and skill! Good job!

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Makes perfect sense to me. One of the things I questioned about the concept of merely removing the seal (as advocated by a UK-based authority) was that the placement of the bearing was not designed for oil lubrication, not to mention that the OEM bearing internal clearances are designed for a much thicker lubricant (grease) and unless there were copious amounts of oil circulating under significant pressure, I would not expect optimal lubrication. That said, most of the OEM bearings seem to last a long time, and it's only a tiny (albeit unknown) percentage that self-destruct prematurely.

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I am not much of a gambler, can't even land 2 matching number on lotto tickets. I rather not take the chance, so I replaced it.

One interesting aspect I found in this gbx is that the pinion bearing was made in Brazil, but the Genuine Porsche replacement bearing was made in Germany --I'd been advised to use only German-made bearings.

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How does it compare to your 993? I just ventured into the 996 world a couple of months ago after 8 years with the 95 993...

Tom, I am the black sheep among the 993 community. Ironically Chris Walrod and I still pretty much work on lots of 993s on weekends but I for one prefer the 996. We always joke around and telling each other "Man, it would be so great to be working on all 996s, because they are so much easier to work on." The only draw back of owning a 996 is the constant ridicule and down talk from my 993 friends. Mechanically, handling, ease of everyday use the 996 is 100% better than the 993. Not to mention ease of repair and mechanic friendliness. I made a decision to sell my 993 and use the 996 as an everyday driver mainly for those reasons. After all who have time to constantly deal with the maintenances, the 996 only requires 1/3 of the 993 maintenance in 1/2 of time to perform them.

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I just sent him a Private Message. Thanks for suggesting that.

Great write up. I am not a DIY'er and my car has been diagnosed with a bad piniion bearing also. The mechanic I am dealing with says it is cheaper to put in a used tranny as opposed to taking it apart and fixing it. He also says that when he removes the parts to get to the bearing " things " usually break and need replaced. Any opinions on my best course of action ?

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Great comments, Robin. It is interesting how much crap 996 owners take from 993 owners... I have to admit I was skeptical about buying a 996, but I am really surprised about the quality, performance and the drivability. My C4 cab is a daily driver as well. It is a MUCH better DD than the 993. I really love the car and all of its fantastic engineering. On the other hand, if I were to have a garage queen, it would be a 993. ...Unless, of course, I could afford a 996 gt3! I actually wasn't looking for a 996- it just fell into my lap. The cab is great- I actually had the top down today in the 43 degree sunshine!

Robin, great DIY. I have tackled a T-10 rebuild in the past but this looks like a lot more involved.

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Scott, I think he was just trying to avoid the option to rebuild the box, it is just much easier to replace the transmission entirely. There is really nothing to break to replace the pinion bearing unless you don't know what you are doing. Maybe he is referring discovering more wear and tear parts that needs to be replaced while you are at it?

great DIY instructions, and nice photos too. does a tip transmission have a pinion bearing ?

Superb pictures ! they make it look so easy ! Respect for putting the transmission into pieces, I had never seen that before on a 996.

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Robin, Thanks for your reply. I also believe he was referring to a used tranny. Wouldn't a used transmission have the same weak bearing problem ? Are there rebuilt ones out there already that have addressed the bearing problem ?

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Prior to rebuilding my own transmission with a new pinion bearing I did a lot of research and found that there are many refurb transmissiosn for sale on ebay. All of them supposedly already had the pinion bearing replaced with a new unit. Not trusting the history of the transmissions for sale made me to rebuild it on our own.

Robin, Excellent thread. Thank you, so much, for posting it. You mention the spider gear as a common failure point for the 996 transmission. Did you replace the unit in your car? Also, what did you use to upgrade the clutch forks? And the final question, did you take a look at the lifters? Any signs of failure? Thanks, Jon

Jon, The pitting on my spider gears were still minor so I left it in, the pitting condition can vary from car to car. Not too difficult to replace. I did upgrade the clutch fork and the pivot point, made a huge difference on how smooth the transmission shifted and the pedal force. Prior my clutch pedal required a lot of force. The lifters looked fine, but I know there were probably a hand full of them that could be replaced as I do hear a little lifter noise at idle but goes away the second I give a little gas. I decided to leave them as they were, again no big deal if I had to go back and replace them. The biggest surprise to me was replacing the CAM chain plastic guides, as now I can hear and feel the variocam working. I didn't replace any spark plug or coils so I know my power increase the engine tone change had to come from replacing the CAM chain guides. Hard to imagine it would make that much difference.

have the part# for the clutch fork and pivot? u replace that tube thing also while u where "in there" ?

Very, very impressive When can I drop my car off?

Awesome, Robin! I can't wait to tackle the same thing myself. I need a garage first. Love the 360 too!!!

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Sorry, don't have the part numbers just called Sunset Porsche and told Jeff what I wanted to do and he knew all the parts that I needed. I didn't replace the guide tube, but I did replace the throwout bearing.

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Jeff is the man when it comes to getting parts. He'll tell you what you need and don't need. I normally give him a list and then he replies noting any discrepancies or newer updates.

Robin, You and Chris make invaluable contributions to this site. Many thanks for your posts!

amazing how well the gears were(n't) worn. And great pics thanks Robin! Hans

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Robin, Are you going to have to drop the engine again to get to the lifters? Are they a replace only or can you clean them out and drop them back in?

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Ed, It is possible to replace the lifters with the engine in, but it would be hard to line up the cam sprocket back to where it was just because it would be hard to see when the engine is in the car. They are not serviceable parts, just need to replace them when they go bad.

Robin, I own a 1999 996 C2. It has just about 106000 miles on it. The check engine light is ON, checked it and it said camshaft sensor, changed it and now it seems there is a difference in the timming angles?? Have you heard about this, I asked if I need to change the timming chains, they said no they are really strong chains but there is probably something wrong with the computer cause it should adjust the angle automatically so I need to reprogram the computer and get it fixed?? Hear about this?? I would really apreciate your knowledge about this, I'm in Bolivia South America no porsche dealers or autorized mechanics, I just imported this car for the US for my personal use. thanks Sergio

What exactly is the code number? If it is the cam position sensor then there is only 3 possible reasons why you are getting this CEL: (1). Timing is off (2). Sensor bad (3)l Wiring bad

That's amazing write-up and pix to document the process. A few questions please if you don't mind as I'm looking at getting into an earlier (2000 MY) 6-speed 996 with high (100k miles) transmission mileage but a low (40K miles) pre-owned engine supposedly due to mis-shift induced valve train damage on the original engine. Experience-wise I have done a few timing belt changes on DOHC engines, have a compressor and impact wrench, and have worked on cars hobbist-style for 20 years. 1. What brand/model scissor lift did you use? Looked like you had to drive the car up on a few planks of wood to gain sufficient under-car clearance? 2. Will the A/C lines have to be disconnected from the A/C compressor when you mentioned "removal of A/C compresser"? 3. Doesn't sound like the various timing, intake/exhaust, IMS chains were replaced in your advanture, any particular reason they were bypassed when you are already this deep in? Same question with the IMS, i.e. replace with the full IMS shaft from LN rather than just the bearing kits? 4. I'm not likely to tackle the transmission bearing myself, and will use someone local since I just do not have the right equipment, roughly how much does it weigh? (a couple of hundred pounds?) I guess the only unknown now is the possible cyliner crack that I've read about, which I understand is irrepairable........ Thanks in advance for the inputs.

I bought an Greg Smith Equipment scissor lift, you will need to use some wood to clear the height so you can drive a car on there. Normally I park a car on there when the lift is not in use. The A/C line will not need to be disconnected just like the 993. But removing the angled A/C compressor bolt can be a little tricky. Easier if you remove the throttle body and guide your socket into the right spot. Because replacing the chain would require the entire engine to be taken apart, which was not necessary in the 100k miles refresh. So I only replaced the various plastic timing chain guide ramps. The IMS bearing kit sufficient enough not need to replace the IMS shaft. Never weighted the transmission, but I would guess maybe 100lb? Engine probably around 400lb. 6 month after the refresh here are some update: We opted to leave the pinion bearing seal out during the the transmission rebuilt, the transmission still shifts perfectly with no ill noise. However I noticed there is a built up pressure inside the transmission, I can hear a hissing sound when I remove the filler plug. The pressure has not caused any blown seal or leaks yet, but keeping my eyes on this. Not sure what would cause the transmission not to vent properly, thinking maybe the thick grease from the pinion bearing maybe blocking the vent hole on top? As for performance, after replace the timing chain ramps I can again hear the engine pitch change when the variocam kicks in and a definitely SOP power difference. My gas mileage increased from 21 - 23 mixed highway / city driving. So far I am very happy with the refresh. Thanks

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I just had this done to my 996 recently and the shop indicated they had issues with pressing the gears off too.

Great work Robin! Thanks for taking the time to post!

Great thread, I did not realize the 996s were easy to work on. That's one of the reasons I've been reluctant to move on from my '88 Carrera. I completely rebuilt the engine down to the crank about a year ago but crappy ac is starting to get really old, even with improvements it's only "decent". Met a guy in my office parking garage who went to a 996 from 14 years with a Carrera and never looked back.

Sorry for reviving this thread, but there is so much great stuff in here that I find it worth to be rehashed. After dropping the engine to address several issues (noisy valve lifters, clutch slipping and 2nd gear grinding), I have been in contact with Chris on the tranny part. He has been very helpful and the gear stacks are in a local shop now to press everything off. Conclusions sofar: The redline shockproof gear oil has done a great job. Pinion bearing looks like new, spider gears are all in great shape. I guess my tranny problem (2nd gear grinding) is due to bad synchros or the 1st/2nd gear guide sleeve. Will find out once I can have a good look at the pressed off parts. I have the timing tools on order and as soon as they are in we'll tackle the valve lifters and maybe the variocam pads. We'll see.. JP

You guys rock! This is one of the best write-ups ever...Thank you so very much for your knowledge.

Hi Robin Great job! I am planning my engine removal on my 02 996 Cab as I need to replace the Oil separator. Did you have any photos you could upload of your ATV jack without the engine on it? I have an 1500lb jack which I use for my Harley, which I was thinking about modifying for the engine removal. By the way nice collection of cars! Nine96 Down Under

Thread revival....Is this car still on this same pinion and working well? Wondering how things went and if the removed seal worked out....