Replace cracked Transmission Casing with new one

1999 911 Carrera The transmission casing was cracked completely around the perimeter. I removed transmission and now have the main casing with the attached gears sitting next to a new main casing on the work table. Tried to attach photo but wouldn�t load past 90%. I�m retired have lift and most tools and equipment. I haven�t researched manual or you tube. Looking for any suggestions or advice on subject. This is a learning project for me so go easy. Cars body work great and I new about mechanical problems. I will replace IMS, Rear Seal, and check for bore scoring. Engine ran fine. Thanks in advance.

OK, I'll bite

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Hey bud, I will indeed go easy! I think you will benefit yourself much more by taking some time to do some independent research on Youtube or on Rennlist. Some search advice for you is to add the term "Porsche 996" to your Youtube searches, and "Rennlist" to your Google searches. For example, on YouTube "Porsche 996, IMS bearing replacement." "Porsche 996, RMS replacement," "Porsche 996, Transmission replacement.", etc. And you will find videos that people have posted that detail these jobs. For Google, if you'd like more to read and more photos to look at, search for "IMS Bearing Replacement, 996, Rennlist" and you will find results that are more specific than simply googling "IMS bearing." It will be tough to find someone on here that will walk you through each step, as you are taking on a lot of big projects. That's a lot of work for someone to sit down and type all of this up for you. While you're doing your research, if you come across anything that confuses you or you have specific questions for the group, I'm sure you'll find people more than willing to help you with specific questions.

Step 1: Remove inside of gearbox. Step 2: Install inside of gearbox to new case. Done. This is a total gearbox rebuild including all set up of backlash and clearances. You need the total instruction manual, a handful of special tools, and the experience of having rebuilt a few other Porsche gearboxes... plus some big *****.

I would think it shouldn't be too hard, unless you have to replace some of the case bearings in the new case (they might be pressed in) also pay attention to any shafts that require specific end float and appropriate shimming

I realize this won’t be easy or if I can even do it. I’m a retired engineer so I know enough to be dangerous. I have the manual and many other options. Once I get all the correct data then I will go to work on it or bring to a shop. Keeps the mind busy. Thanks

Do it! Document it and post it up here as you go. That’s what I’m doing as I refresh my ‘02 targa. I’m like you, recently retired and tearing my car apart for fun and prof... ...oh wait, forget that last part.

Here is a manual: http://p914-6info.net/996_Manuals/99...ion-Manual.pdf Full: http://p914-6info.net/996%20Manuals.html

There is no published manual that I know of for the 996 transmission, the one posted above references the G50 in a GT3. It is a straight forward swap of the drive case but the tail housing is a little fiddly to reassemble. the problem you face is the pinion depth will be different and you have no way of measuring it. You can reassemble it reusing the old shims this will get you close and adjust the side bearing shims to get the backlash correct. If it were me and a one off repair I would leave it to a pro and send it to California Motorsports. The first one I repaired I had the luxury of having two transmissions if front of me and I also do a lot of trans work so I could fall back on previous experience as far as dementions go. With the lack of a proper manual I would send it out.

Why not take an easier route and replace the trans complete with a good used one. Since you already have the old trans out of the car, you already know you have the ability.

The problem with a used trans is the unknowns, A lot have bad pinion bearings or bad 1-2 or 3-4 syncros I consider any used trans a core and disassemble and inspect.

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If you are really itching to do a gearbox, I would do this: The quote below is correct. This is the devil you do not know. The only way to avoid it is to buy a rebuilt transmission with a warranty, or rebuild it yourself.

Whatever I do on this car it will always be new Porsche Parts. When I am done with this car hopefully this year I will enjoy driving it knowing I did the work. I will then look around and buy another 996 with mechanical problems and whoever buys the 996 I’m working on now will get the best of everything. I raced Formula Ford, Formula 2000, and SRF, till I was 65. I have experience changing gears on the formula cars and also set up. Mechanical stuff different story. I joined PCA so I can take a ride around tracks I used to race on, but not competitively. I hope to redo 10 996’s at one a year so when I’m 83 I will be well educated and experienced in 1999-2005 911’s. All suggestions and advice is greatly appreciated. This first 996 makes me smile and I can talk to her without any talk back.😄😄

Amen…😄

I've tried nothing and I'm all out of ideas!

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no shortage of broken ones,

The advice I can give you is this: find an experienced mechanic that has done at least 5 of these rebuilds. Find out which mistakes, service manual omissions, wrong data, tips and tricks, and other things that will save you. The simple fact is that the first time anyone does anything, it�s probably wrong. Best to learn from mistakes of other transmissions you don�t care about. I rebuilt a transmission once. Had a lot of trouble before I found out these tricks. And that the manual left out a couple of important parts. Once you know these �secrets,� you�ll end up with a good rebuild.

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Love it! At least we know that there will be 10 more refreshed 996s out in the market worthy of ownership. Hope you document it well on YouTube, and rennlist!

I'm considering something similar, I found a g96/01 with a busted bellhousing to repair my g96/00 which has a very slight whine could be pinion bearing. I'm not sure if the 00/01 bellhousing are identical? Anyone know? I found a good video of the gearbox internals: You Tube EDIT - scratch that, the gearbox I found had a big hit and looks like the input shaft is bent, no bueno

If the cracked case section is the differential carrier, you are jumping into the deep end of the pool in replacing it. The factory WSM as linked does not describe servicing the G96 in any depth, as another poster has mentioned. Unless you are very clever in removing the pinion and input shafts, you will destroy the seals on the pinion shaft bearing that sits in the differential carrier. And you will inevitably destroy the seals on the input shaft bearing that sits in the diff carrier. As others have noted, you will need to remeasure and reestablish correct pinion depth (shims) as well as shimming for the input shaft bearing just mentioned. If you need to replace that pinion shaft bearing, you will need a 50-ton hydraulic press to remove the gears from the shaft. I could go on, but you get the idea. The G96 is the most difficult Porsche transmission to rebuild, just a royal frickin' pain. I think the reason the WSM doesn't describe it's service operations is that Getrag and Porsche were just too embarrassed by the mess. I mean, interference fit for the gears on the pinion shaft rather than splines like every other transmission, who would design anything like that? Crazy. By way of contrast, the successor to it, the G87, is night-and-day easier to service. Cheers,

This requires a level of expertise way beyond what is normal DIY. Call them http://www.gboxweb.com/

Thanks.