997.1 C4S RWD conversion

Long story short my 07 C4S has gone through 3 sets of front inner CV boots in 40k miles. Why this is occurring is what I plan to find out. First as little background. I purchased this back in 2018 from a private seller in Jacksonville FL. The car was first ordered by a Brumos Porsche family member to their specifications (C4S black with sand interior, carbon package and little else) When it arrived to Brumos they installed a factory aerokit along with H&R springs. The second owner added the F77 engine package from Champion Motorsport (Werks air box/plenium, Tubi exhaust headers, Tubi mufflers, GIAC software). I then purchased the vehicle. Now the 997.1 C4/S AWD system is purely mechanical and can be removed. Many 996 owners have done this. Since this is a completely reversible mod, I plan on converting my car to a RWD while I analyze the root cause of my tearing CV boots at my own pace. This will also give me the opportunity to learn a new skill (replacing CV boots) Parts ordered: IMG_6846.jpeg (1.99 MiB) Viewed 8794 times IMG_6847.jpeg (2.8 MiB) Viewed 8794 times First order of business will be to procure a 340 ft/lb torque wrench for the Axel nuts....

Interesting project. Looking forward to updates. Harbor Freight sells a 600 ft lb Icon torque wrench for $400.... And here's one on Amazon for $169... https://www.amazon.com/SuZhi-1-Inch-Dri ... 77858&th=1

I never pass up the opportunity to purchase new tools. Technically it save me money… I may stop by the university and talk to the mech-e department. They have quite the selection of tools also. Mike

Decided to buy a underhoist support stand as Ive been meaning to for a long time and just never pulled the trigger. I had to find one that fit under my maxjax (48” lift). With that being done and finding a torque wrench i could borrow when I need it, i started the project. Removed the under panels. IMG_6859.jpeg (2.42 MiB) Viewed 8732 times IMG_6863.jpeg (2.22 MiB) Viewed 8732 times IMG_6865.jpeg (3.99 MiB) Viewed 8732 times As in all projects I discovered a potential issue.. IMG_6860.jpeg (4.04 MiB) Viewed 8732 times Yep thats my transmission mount insert. Well part of it anyways. That sent me to Function First for their aftermarket products. I ended up going with their Orange insert (softest) to get as close to OEM as possible. Fantastic customer service also. So while I wait for the insert to come in I’ll start disassembling while at the same time clean up my weeping RMS.

Looking forward to following along with this!! My 992 has bumper to bumper under panels too. It never dawned on my until seeing that picture how nice and clean they keep the under-carriage. Looks like a brand new car under there! Curious why you opted for an aftermarket transmission mount?

Honestly i don't have a compelling reason besides wanting to see for myself if I notice a difference in NVH or shifting behavior. The cost is low enough that if I don’t find it to my liking I can easily switch it out back to OE. I was surprised that the OE version was done after 39K miles. I did find some chip and seal rocks on top of the under panels but I agree it does look nice and clean! I’ll get my steamer out and scrub the rest at my leisure! Mike OPS

Well that was actually one of the more straightforward projects Ive had. Remove gas tank straps and the V-brace to gain easy access to the inner CV boot. Remove the inner CV boot from the Diff: IMG_6876.jpeg (2.88 MiB) Viewed 8661 times I then went to the back and braced the transmission: Remove the bracket - watch your transmission mount insert crumble to the floor. Sweet. IMG_6879.jpeg (1.81 MiB) Viewed 8661 times Remove the 3 bolts on the guibo. Now I went to the front and removed the nuts and then the long studs holding the front diff. It needs to be braced to do this as it will now be ready to lowered after the next step. Remove the center bracket but first remove the 15mm bolt on top and set free the coolant lines. IMG_6881.jpeg (2.46 MiB) Viewed 8661 times Now with the help with a friend lower the whole unit out (sans axles - they are still held in by the axel nut and pressure) IMG_6884.jpeg (1.8 MiB) Viewed 8661 times Next use a punch to smack out the axles. A couple good whacks did the job. IMG_6885.jpeg (2.47 MiB) Viewed 8661 times IMG_6886.jpeg (918.73 KiB) Viewed 8661 times Ended up being about 78lbs. Time to clean up the front (Those are the studs that held up the diff) IMG_6890.jpeg (2.89 MiB) Viewed 8661 times Front end sans diff: IMG_6891.jpeg (2.73 MiB) Viewed 8661 times IMG_6893.jpeg (2.12 MiB) Viewed 8661 times To do list: Clean up the back. Put in transmission mount insert. Torque axle nuts to 340ft. lbs. And figure out how to protect this in the meantime. IMG_6892.jpeg (2.12 MiB) Viewed 8661 times Overall fun job!

Awesome work! Like so many things on the internet, you make it look so easy and clean. Why no greasy mess at the end of the CV joints? -- must be new-fangled parts I'd be happy to design and 3D-Print a bolt-on cover for the flex joint stub if helpful -- would just need some dimensions, etc. To a hammer, everything looks like a nail. To a 3D-printing guy....

Tom, you read my mind! My friend and I were saying the exact thing. "this looks like something that needs to be 3d printed". Let me study it and get back to you. I have to figure out which design would work the best - a complete cover that bolts onto the guibo through the m10x1.5 threads (with nylon bolts) or something smaller.. preventing oxidation can accomplished with some grease and a cap. Sorry just thinking out loud here. As for the grease it was already flung all over when they ripped in the last 3K miles :-/ everything else (diff back) is covered by the body panels. I will clean up the back where my RMS is seeping... Mike

Does it spin? That would push me toward the bolt-on version, unless that shaft end has a threaded hole?

I’ll have to check it out tomorrow and get right back to you!

Also thinking out loud, one thing I've done in the past to seal a catalytic converter in storage was to use steel spacers in bolt holes. The spacers were a mm shorter than the plastic, so that the bolts could be torqued against the insert, compressing the plastic to form a good seal.

Very interesting - do you happen to have a pic? what about recreating the guibo? (minus the bolts there of course as those attached it to the driveshaft) IMG_6901.jpeg (2.52 MiB) Viewed 6255 times

Ok here are the torque specs for this project: (attached shop manual) Fastening screws between drive shaft and transmission flange; 29 ft/lb, 13mm Retaining strap securing cover to body; 17 ft/lb, 13mm Diagonal brace to body; 74 ft/lb, 18mm Stud on front-axle cross member; 15 ft/lb, 7mm Fastening nut on stud; 48 ft/lb, 15mm Fastening screws to securing pipe holder to body; 48 ft/lb, E14 Transmission bracket to body; 48 ft/lb, 16mm Transmission bracket/support to transmission mount; 48ft/lb, 15mm RWD Conversion.pdf (5.49 MiB) Downloaded 295 times

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Sorry, I don't have a pic handy since that cat is now back on the car. You can get steel spacers at most hardware stores. The idea is to make the hole just big enough for the insert, and then make the plastic maybe 1/2mm taller than the insert, so that when you torque the bolt, it will compress the plastic to create a good seal, and torque down against the metal insert so you don't have to worry about it backing out like you would when torqueing against the plastic alone.

Makes me think that just recreating the guibo with just the three empty holes and then adding a cap where the rod can spin freely would work...

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Sounds about right to me.

Maybe something like this. cap.jpg (162.4 KiB) Viewed 6214 times

bingo!!

Added function first transmission mount inserts. I went with orange which is their softest. Pretty straight forward directions. Now all I'm waiting for is two new rear tires (tomorrow) and the torque wrench (tomorrow). Already cleaned up the panels and all undercarriage. Should be done this week. IMG_6918.jpeg (1.72 MiB) Viewed 6199 times IMG_6921.jpeg (2.75 MiB) Viewed 6199 times IMG_6922.jpeg (2.9 MiB) Viewed 6199 times IMG_6923.jpeg (1.93 MiB) Viewed 6198 times

Was able to get the new rear tires mounted and everything back together. Used a torque multiplier I borrowed from my friend who owns a tuning shop. Got the axel nuts torqued to 340 ft/lbs. Took it on a very short drive and the steering is definitely lighter for a lack of better terms. It is especially noticeable on slow (driveway) turns. Im really really liking it. IMG_6927.jpeg (2.94 MiB) Viewed 5810 times IMG_6928.jpeg (3.01 MiB) Viewed 5810 times IMG_6929.jpeg (2.17 MiB) Viewed 5810 times Im hoping this helps the next person who tackles this very simple job. Next up is the CV boots... Mike OPS

Very cool project and appreciate you sharing here on Carpokes!!

Glad I could give back! I'll be interested in talking more about 3d printing a part you mocked up! Mike

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Absolutely, wasn't sure if you were planning to do it yourself, but I'm more than happy to design and print it. Without the parts in hand, it may take a couple of tries. I'd need as many dimensions as possible to start...

Rgr that! I have some ideas on how to get you the measurements to make it easier - Thank you for the offer! Mike OPS

Thank You for the VERY entertaining and educational project - pictures - commentary . I have avoided the 4WD 996-997's because I just figured "more moving parts = more things to break". Now I can think "outside the box" about them....

Well after 35 Porsches I am glad I was able to help you out. It is astonishingly simple to do (with the right tools!) Mike OPS

Great tutorial thread...thank you for expanding my knowledge base.

Tom, I have a thought (scary as it is). What if we just use the guibo as a model to make the part? https://assets.ecstuning.com/product_li ... _x800.webp I was going to buy one and have it shipped to you. I want to replace mine anyways! Mike

That could work, although I'm not 100% sure I could mirror the flange with just that part. Maybe, probably, but until I have it in my hands.... I don't suppose the flange comes off easily, does it? Ideally, I'd have that in hand so I could model a perfect cover. If that's not an option, I'm thinking the old flex disk might be better than a new one, as it may have indents or wear/grunge markings showing exactly where the flange was. I'd also need to know how far the shaft sticks out and its approx diameter. Alternatively, if you wanted to install the new flex disk, I could probably model a cover to bolt to it, rather than to the flange...

The hole in the center of the guibo is the diameter of the bearing on the driveshaft. The little pin goes inside of the bearing and is approximately the hight of the guibo’ a depth. Here are additional pictures. IMG_6974.jpeg (2.12 MiB) Viewed 10005 times IMG_6975.jpeg (2.78 MiB) Viewed 10005 times If we create a dome for the shaft like your original design I believe that would work? Mike

Willing to give it a shot. Worst case, we may need to iterate a bit if the first try isn't just right. Shoot me an email or PM to get it going.

Awesomeness

No indications where these failing CV boots were sourced. I went thru this problem a while back on an '04 BMW XiT wagon's front CV boots. They kept failing after a 1000 miles or so. These were remanufactured from a reputable supplier ($) but kept failing. The problem was eliminated by buying brand new OEM CV axels from BMW ($$$$). My supplier covered the replacements on the remans but the labor replacing the units over and over got old. Just my experience.

They were bought from FCP Euro and were Porsche brand. Im almost sure its going to be the chip and seal aggregate…

Sorry it's been a while but working on your cap/cover now.

Hey no rush! Just took out my car for the first drive after hibernation and she has a random tick I now have to source! Stuck lifter or gravel on the heat shield are my initial thoughts.

Here's a quick print of a cover that fits the flex disk. I designed it to use steel inserts, much like the flex disk, so that the bolts can be torqued to spec. While you can torque on the plastic, there's a risk of breaking it, and an even bigger risk of them coming loose as the plastic compresses over time. The inserts are about $2.50 at McMaster so will add them to my next order if this looks like a go. I had to guestimate is how tall to make it so it clears the shaft stub sticking out. I hopefully erred on the tall side. One thing I noticed while doing this is the shaft will not be entirely sealed off from the elements, since there is a gap between the flange and the flex plate. Same must be true of the factory configuration. But this will protect it from road debris/rocks, etc. to the same extent it was protected from the factory. Let me know if you see any issues, otherwise I'll get the inserts so you can give it a whirl... g11.jpg (254.7 KiB) Viewed 9602 times g22.jpg (325.66 KiB) Viewed 9602 times

Hell of a job! I agree with the metal inserts as I will torque the bolts to an extent with the added security of locktite like it cane from the factory. That dome will be plenty to cover that little shaft also! I say full send! Attachment point. IMG_7172.png (9.78 MiB) Viewed 9470 times Mike

Finally made one with the inserts. Looking at that picture above, you may need to put washers in the recesses above the holes, so that the inserts on the cover can be torqued against metal. guibo-cover.jpg (950.36 KiB) Viewed 3843 times

Bravo! Your skill at this is definitely showing in this work!

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I can't find your address now. Can you re-send it to me, and I'll get this in the mail.

Done!

Update! Received the 3D printed driveshaft cap (not sure what to call this part) from Tom: IMG_7582.jpeg (431.29 KiB) Viewed 6887 times Took out the 16mm bracket bolts and loosed the transmission ones (15mm) (took the top one off to swing the bracket down) IMG_7576.jpeg (2.78 MiB) Viewed 6887 times Installed the cap after applying a little plastilube on the exposed metal, I used the factory bolts and snugged them down. I opted not to use any blue loctite as the factory did not. Looks like a great fit! IMG_7578.jpeg (2.19 MiB) Viewed 6887 times IMG_7579.jpeg (1.75 MiB) Viewed 6887 times Torqued the bolts to 48 ft.lbs and put the bottom panels back on. Broke two studs in the process so I have another project…. IMG_7580.jpeg (2.24 MiB) Viewed 6887 times Mike OPS

Looking good! Did the metal inserts make contact with the metal on the flange? If not, I'd put some washers in there. If the plastic is bearing the brunt of the torque/compression, the bolts will eventually get loose and the plastic permanently deforms/compresses. Or put Nylock nuts on the back side. And I love the sticker.

The torx bolt flange was making contact with the insert’s, combined with the low torque value, makes me believe it will be good to go! I tell you those 16mm brace bolts Im getting a little shy of taking them on and off as if they break, it wont be pretty! Mike

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Right, there's no problem on the side with the bolt head. I was talking about the side where the 3D-printed part mates to the car. If that side is plastic on metal, I'd recommend putting washers in the flange recess to ensure you are torquing metal on metal.

Copy! If i had to guess the majority of the stress will be generated axial; What I will do is check up on it after a drive or two!

This thread is awesome. There are so many wrong information out there that actually seeing it done is priceless. I ordered everything you’re showing on the first post and one it gets here will get to work on mine also. Reading on Rennline it says the following: On 997.1, Front diff must be retained or electrical portion of electrohydraulic clutch must be modified. Did you had to do anything on the clutch? I recall seeing your driveshaft and front differential on the floor. @Tom is you still have the file and willing to print me one I’ll happily buy it from you. Thanks Filipe Thanks

Filipe, Glad it has been helpful and I can help you through the process once you start! Rennline I believe has a typo as it should be the 997.2. Our 997.1's have no electronic connections and is an old "dumb" system. (and yes it's still on the floor and I have not rebuilt the CV boots yet.....) Hey I would grab the transmission mount insert as I would bet yours will fall apart like mine! Toms cover has worked flawlessly after 500 miles. I will make it part of a check when I change the oil but so far so good (hell of a job Tom!) I am getting an alignment done one the 18th and will post the results. Mike

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I just posted the 3D print file for the cover in our 3D-print section. See link below. If you can't find someone local to print it for you, feel free to email me. viewtopic.php?f=20&t=4137&p=46288#p46288

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Do those stub axles work on the 4wd upright? My understanding is the 4wd has the abs pickup on the larger diameter of the cv joint, not on the spindle.

Mark, Yes those stub axels work on my 997.1 with no problem. I think the confusion is in the difference between the model years. For example here is a pic of a 996 turbo (from pelican) front axel. Notice the "teeth" on the axel. IMG_7885.jpeg (1.92 MiB) Viewed 2688 times And now look at my front axels: IMG_7882.jpeg (3.07 MiB) Viewed 2688 times Notice how mine are smooth which matches the stub axels purchased. The wheel speed is picked up in the bearing (I believe) hence the reason I do not get any ABS codes. If this didn't work, my car would be very upset thinking the wheel was locked. Today I am getting her aligned! IMG_7891.jpeg (3.3 MiB) Viewed 2688 times Mike

Thanks for confirming. Much appreciated.

@Maruscmn Love the shot from that angle!!!!!

@ROB III , Thanks! Now look how bad my toe was! Im supper embarrassed to say I have never had an alignment since I bought her in 2018! IMG_7907.jpeg (2.74 MiB) Viewed 2662 times

You will likely get better tire wear or at least more even tire wear side to side. If it was driving fine and consistent, possibly human nature to assume all is fine....if it ain't broke, don't fix it.....but now you know it needed some adjustment. The question is will/did it feel any different? I find the rear toe before the more alarming given weight distribution. But overall....its progress!

the rear toe was way, way out of spec - I would notice a "floaty" feeling on sweepers but I honestly think the car is so good it was covering it up. Mike

Update: I thought I would get the front CV boots rebuilt this summer but time got away from me! I have some good milage on the conversion and all is good! Enjoying this way too much...

Another update! Toms 3d printed cover is working like a charm and is in perfect condition! IMG_1639.jpeg (2.88 MiB) Viewed 1387 times IMG_1629.jpeg (2.12 MiB) Viewed 1387 times