torque spec for bolts in the bell housing

After about 18 months of ownership, it is time to separate the tranny from the engine to see what kind of IMSB I have. It is a 1999 with a factory remanufactured motor installed by the dealer in 2005, so I may have the small single bearing, or a non-replacable big single bearing, there is only one way to find out. The first engine lasted 45k miles, this engine now also has 45k miles, so I�m getting a bit nervious. I started this afternoon by first disconnecting the half-shafts so I can get to the bolts in the bell housing. Pelicanś says I should have all 16mm bolts + one 13mm and one triple-square. Looks like I have 16mm bolts, one 19mm bolt, one 13mm bolt, and one triple-square. I didn�t manage to break any of the bolts free, I�ll need a longer breaker bar I think. What should be the torque to these bell-housing bolts? Just trying to see if they should be this tight to loosen, or they�ve been red loctited. Thanks

You can get the porsche technicians manual on disk from eBay for about 30 dollars, it's not like a diy manual it's made to be read by trained techs but I used it along with advice to rebuild my engine. If the bolts seem tight try some sort of spray release oil , give it a goof spray and leave it to soak for a couple of hours then go steady maybe with a longer bar, be careful not to strip or snap and bolts , it's the worst thing ever! Not sure of the exact torque but they with be quite tight mating the engine and box is a crucial area!

I'm not sure what you'll gain by a visual inspection of the IMS bearing, other than seeing what you'll need to do to replace it. There isn't a whole lot to see once you remove the flange, and very little to no guidance on how to know if the bearing is good or not, unless it is badly physically damaged or worn out to the point of major failure. What you are doing is a lot of work, and if it is a 2005 engine code reman engine, isn't the general consensus that you should have the newer one that you need to split the cases to replace the bearing? That being said: I highly doubt anyone in a professional shop (or even a knowledgeable shadetree) would use red loctite in those bolt positions. I use a regular 1/2" ratchet, but if you can't break them loose, you could use a breaker bar. in my experience, getting at the top bolt(s) is easier if you drop the front transmission mount a bit to make some room to work, and approach them with lots of extensions from the front of the transmission. Bolts aren't measured by the size of the head, pretty sure all of the bolts except that triple square are the same diameter, but have different lengths. The position they are installed in matters a lot. To help with this, I keep a piece of cardboard nearby, mark it for "up" and poke holes in it for the relative position of the proper bolts to make reassembly easier. You may want to consider some spare bolts in the same metric size to use as guide pins and for reinstallation. Aligning the transmission input shaft and the clutch disk is tricky if you don't do this because of the angles involved and weight of the assembly. It's challenging with the engine/transaxle on the bench, and twice as tricky when it is in the car since you can't see everything. I have used bolts to progressively pull the engine and transmission together once I had things aligned. Once you remove the IMS flange, make sure you have the correct sealing products to reinstall it. They were mail order for me. Not sure what your local supply house situation is like, but there are sealants that aren't garden variety loctite products. Once you remove those bolts, you need to replace or reseal them, since they are open to the inside of the case. If you're removing the flange, you should consider replacing the flange seal. If its a manual transmission: You're taking off a flywheel and clutch, so don't forget new hardware for reinstallation. It is stretch to yield and not meant for reuse. Inspect the RMS, dual mass flywheel, clutch, clutch input seal, throwout bearing, check for updated clutch arm pivot, IMS flange seal - think about replacing other stuff while you are in there since the labor is about the same, it's just a few more parts. Consider reinstalling the slave cylinder before reinstalling the transmission. It can be a bear to get right installing it in place with the transmission installed. Have a clutch disk alignment tool handy. Insect all of your mounts, the front transmission mount is a lot easier to replace out of the car (unless you have the special aftermarket tool to do it in place). Last of all, I personally wouldn't do this job without a lift and a transmission jack. I also used an engine holding bar that I fabricated. Could you do it without this stuff? Sure, but I wouldn't want to.

i think i will follow this one

63lbs on all bolts except the one with a nut is 33lbs. The 996 Torque guide is the best $60 you'll spend if you are going to be wrenching on these much. https://lnengineering.com/education/...utomobile.html

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I can't believe I haven't heard of this until now. It would have been on my Christmas list.

How much can you tell by removing the flange cover? Original vs. retrofit? Single vs Dual vs larger single? Do you need to set to TDC and timing locks just to inspect if you don't remove? Charlie, lol! Mine is absolutely tattered, black with grease, and the pages have all come loose from the binding. It's so dang handy!

I'm no expert, but if I were taking off the IMS flange to inspect the bearing, I'd take the tension off the chains by removing the tensioners, so I'd lock the crank pulley at TDC and lock the cam with a locking bar. I've got that book too. It's money well spent so you don't have to go digging all over hell to find the specs. I did this inspection with a used engine I bought, and I can tell you first hand, there isn't a ton to see.

This is the boat I'm in.

I was under the impression that you can tell whether you have single row, double row, or the larger non-replaceable single row by looking at the IMSB flange without removing it, no? The previous owner put in a singlemass lightweight flywheel that I�ve read can be harmful to the engine crank, so I want to replace it with the stock dual-mass so I don�t get the diesel clatter when idling. Too bad the flywheel and clutch are only 10K miles old, I wonder if I can simply put in a LUK DMFW and keep the old clutch. So removing the tranny serves two purposes for me.

I don't know of any reason why you couldn't reuse the clutch. I know Jake hates the LWFW but almost all of the SP996 racers use them and don't have any issues with them. That being said, on the street, it's something you either like or you don't.

If you are replacing the flywheel check out parts geek, they seem to be most cost effective, I used Jason at Warehouse 33 for mine as Parts Geek don't ship to Canada or "PO Boxes", Jason (the nice gent who runs Warehouse 33) reckoned they were below his cost price. I looked round as I was considering a lightweight flywheel, but went with the DMF as I want the most reliable engine I can build (for the money).

I picked up a Sachs clutch kit and a LUK dual mass flywheel - original equipment manufacturers. I ordered them separately from different vendors and saved a couple of hundred $$ over the big name parts houses for the same part.

I'll definitely need a DMF flywheel, so will check out the various lower price LUKs. Seems like ebay also sells them a few hundreds cheaper. I managed to loosen all but the triple-square bolt (dont have a triple square) and the bolts at 12noon and 1o�lock (I cant even see the bolt at 12noon, but I know it is there). I think these two bolts will be a bear to loosen, any helpful hints would be appreciated. After all bolts are loosen, then it is time to shop for a transmission jack, tools to lock the flywheel, ...etc. As long as I can get the car back together by Feb I�m happy. Thanks for all the help you guys have given so far!

Get a transmission jack first. You'll use it to remove the bolts. I have a cheap harbor freight version, with the typical coupon it was well under $100 shipped. Put your transmission jack under the transmission, remove the bolts on the front mount and lower the transmission end down, then go at the top mounting bolts with a 1/2" ratchet and lots (several feet) of extensions, you'll be doing yourself a big favor. Flywheel bolts aren't hard to remove. You don't need to buy a special flywheel locking tool - you can make one with a short length of steel strap, drill a hole in each end, use an old fastener you removed from the pressure plate to attach one end, and one of the transmission mounting bolts to attach the other end. That'll prevent the assembly from turning. Reinstalling the flywheel requires a torque wrench and an angle gauge (or a sharpie and good approximation if you are trying to save a buck). You probably want to pick up (buy/rent/borrow) a tool kit to replace the IMSB - or at least some of the tools: so you can lock the crankshaft and the cams. If you buy the tools separately, make sure you have the right version of the cam locking tool - the 3 chain and 5 chain versions use different locking tools. The LN kit (and copies) have both. If you don't lock the cam and take out the tensioners you could be making trouble for yourself when you remove the flange. My 2 cents is to buy the right triple square tool, so you don't mess up the fastener. You can get a Lisle kit ( Amazon Amazon ) at Sears or your local FLAPS or Amazon that has a full set of triple square bits. Or find a good tool truck/Amazon and buy only the one you need. Oh, and personally, I like to replace bits while I'm in there, so don't forget the aluminum sealing rings & o-rings for the cam chain tensioners; plus a few green cam caps.

I think autozone has triple square in stock. For the two top bolts, I've used a 16mm box wrench if they are torque'd to spec while basically hugging the tranny. I've also used a series 3/8 extensions with u-joint adapters.

Also, once you get the tranny out, you can replace the AOS without having to take anything off the top of the motor. It still sucks, but 100% possible, and worth doing whenever you are near it.

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My second attempt at loosening the top two bellhousing bolts didn�t work, so I think I�ll do what you suggest which is to get a harbor freight transmission jack, disconnect the front transmission mount and lower the front of the tranny to get a better angle to remove the top bolts. Question: Will I damage the two engine mounts when dropping the front of the tranny so the engine/tranny combo points downward, or do I need to loosen the engine mount to prevent damage. If I loosen the engine mount, by how much ? I don�t want to lower the engine too much and stress out the various coolant, fuel, and brake hoses that are connected between the engine and the chassis. Thanks!

I�m gonna declare partial victory. After dropping the engine at the engine mount for about half an inch, and disconnect the front transmission mount, I was able to loosen the top bell housing bolt. So the only bolt left is the triple square, so once I get a triple square bit the bell housing should be done. I also took out the hydraulic clutch slave cylinder, the shift cables, and the backup light switch, so they tranny is ready to come out once I get a triple square bit and a harbor freight tranny jack. Anything else I need to worry before trying to pull the tranny out?

Nice work! I had the sway bar, diagonal support bars and aluminum crossmember out. Not sure you need to, but I prefer having space to work. Two other things come to mind: 1) make sure the engine is supported from below - once you take out the transmission, it isn’t supported from the front - so it would be hanging from just the motor mounts at the back of you don’t support it. There is a special engine support tool that mounts in the sway bar mounting holes, but if you can cut, weld and drill, you can make one pretty easily. I do my work on a lift, so having a jack under it doesn’t work for me when I change heights. 2) make sure the car is lifted high enough that you can roll the transmission out. Easy enough to change later when on a lift with the engine support bar in place but not so easy if you are on jack stands and your engine is supported by a floor jack...

the IMSB flange says 99602406 Fedex delivered my HarborFreight high rise transmission jack Saturday afternoon, just so that I have something to do on Sunday :-) So the tranny is out after an hour or so after removing the bell housing bolts. The inside look really clean, not much brake/clutch dust. I stopped after dropping the tranny, I will start removing the clutch and flywheel in the next few nights. I can see that the IMSB flange has part number 99602406, with a large nut. Do I have the large single row bearing?

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Slakker, do SP996 racers use the stock clutch plate with LWFW? I have the AASCO LWFW, and what looks like a stock clutch plate (without springs), so there is no damping between the engine and the tranny at all. Do you know if LWFW should be mated to clutches with springs so that there is at least some damping/decoupling? My tranny has rattling noises at idle when fully warmed, which I�ve read is normal for LWFW, but it also makes funny roars when slightly lugging the engine at 5th or 6th gear (2-3k RPM, slight load), as well as in 2nd and 3rd gear when engine braking. It is possible that the tranny has problem, but I wonder if the noises are due to LWFW with springless clutch, and can be alleviated either with going back to dualmass FW, or switch to a clutch with springs.

Unless it is a dedicated race car, I don't see the point in having an driveline without some sort of dampening. Either the DMF or a clutch disk with springs can work acceptably. In my limited experience (race car with lightweight flywheel, four puck ceramic clutch with no springs) driving without some sort of dampener is a PITA. It is like an on/off switch, which has its merits while racing, but takes away any civility in starting from a stop in daily driving situations or easing shifts. I don't suspect it is all that healthy for the drivetrain, but that is intuition, not engineering speaking.

I agree that it is almost pointless for a street car to have LWFW given all the noise and vibration that it transmit to the transmission and rattling of the gears. Even though my car is just an occasional weekend autocrosser (I think I've only driven it a handful of times non-autocross in my 18 months of ownership), I'm going to switch back to the DMFW. Now my next move is to select a DMFW. Looking at pelican parts, partsgeek, ..etc. It seems like LUK makes several flywheels for 1999 Carrera, I don't know which one is correct, I'm leaning towards DMF-024 but it doesn't seem to come with a pilot bearing and I don't know what pilot bearing to go with it. I couldn't find any useful info from the LUK website. From googling around I'm pretty sure I have the large single row IMS bearing similar to the ones in M97 engines, should I open up the IMSB flange and remove the bearing seal as Jake Raby recommends, or just leave it alone and not risk screwing up a working bearing since the failure rate of M97 IMS bearing is low? Thanks

Not sure about your car, but my 2000 C2 six speed used the DMF024. The pilot bearing was pre-installed in the new flywheel as delivered. The Sachs clutch kit I used (K70246-01) includes the clutch disk, pressure plate, throwout bearing, packet of grease and a centering tool. Don't forget new bolts for attaching the flywheel to the crank, and bolts for attaching the pressure plate to the flywheel. They are one time use. I don't have any useful advice about your IMSB. Opinions seem to vary. I googled the part number you posted earlier, and it looks like you have the larger model bearing that requires the case to be split to R&R. if it were me, I'd also be torn between leaving it alone/not risking leaks, and pulling the flange and removing the grease seal. Sorry, but I'm no help.

Sorry for the slow response. I know you are going back to a DMFW but to answer your question, no, the SP996s I know of do not use the spring plate with LWFW. And yes, I've also read someplace that you should, but it seems to work fine without it.

I strapped down the crankshaft with a couple of nylon tiewraps and that was enough to allow me to undo the flywheel bolts. The aasco flywheel is a work of art, too bad I don't like the way it made my gears rattle. Perhaps if I had springs in the clutch plate things would have been better. Ordered a LUK DMF024 this morning. I've never driven a watercooled 911 except mine with the aasco flywheel. I hope the DMFW will not turn the rev happy engine into a slug.

Mayday1, thanks for the great thread. I need to pull my transmission for a rebuild and this has been very helpful. Did you end up using an engine support bar to hold up the back of the engine when you pulled the transmission? Or did you use a jack? I'm debating which way to go on this.

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I am using a scissor jack to support the engine. I wish I have an engine support bar though. While I'm swapping the flywheel, I may want to remove the IMSB grease seal and replace the AOS. To remove the IMSB grease seal requires me to drain the engine of oil before opening up the IMSB flange and removing the chain tensioners. Currently with the engine supported by a jack it is hard to drain the engine oil without make a big mess since the jack is in the way. Do you have a simple design for an engine support bar?

If you google it, there are engine support bars available for purchase, and some pictures of them marked up with dimensions. https://www.google.com/search?q=pors...w=1680&bih=862 The Part number is Sir tools P254 or 9624/1. It mounts to the four threaded holes where the swaybar normally mounts. I made one myself with some angle iron, square tubing and some nuts and bolts. If you can measure, cut, drill and weld, it's easy. Picture in the middle of fabrication (after this, I drilled a hole in the middle, welded a nut to it, and used a bolt to adjust to the bottom of the engine).

I can cut and drill, but I don't know how to weld. But I'll look at your picture to see if I can build something similar without welding. I'm leaning towards just leaving the IMSB alone (not removing the grease seal), it'll save me from building an engine support, camshaft lock, getting new IMSB flange bolts, rubber seals, ...etc. How difficult is replacing the AOS from under the car with the engine lowered a couple of inches? Can it all be done without removing starter, alternator, intake manifold, ...etc? BTW. The dual mass flywheel arrived. 25.5 hours from ordering online to arriving at my door. It is really heavy compared to the AASCO, I'll have to get out the bathroom scale to know the difference.

I found the engine support tool here for $193: https://www.handsontools.com/SIR-Too...r_p_62893.html I'd rather make it myself and save the $200 but welding is a bit beyond my scope as well. Maybe we can design one that can be bolted together rather than welded.

There is definitely no magic to it, no welding required. You could easily bolt the pieces together, and have it work perfectly well. This was under $30 in steel from the hardware store (way overpriced in small sections). I just welded it because I have a welder and it was easy to zap it together.

My bathroom scale says the AASCO LWFW with flywheel bolts weigh 13 lbs. The Sachs pressure plate + clutch also weigh 13 lbs. The LuK DMF024 without flywheel bolts weighs 29lbs. Huge difference. Someone should us make a dual mass light weight flywheel!

I found an example of an engine support took that is bolted together here: https://www.renntech.org/forums/topi...e-support-bar/

You just need a piece of angle iron and a cutting torch to make an engine support.

I just used a couple of jack stands with a 2x10 to support the engine while I was replacing the IMSB. The metal brace would have been nice - but not necessary.