Video of my knocking issue

Well I decided to make a video of it instead : You Tube I can really control that clunk knock with the throttle so easily. I've replaced the rear engine mount, tranny mount and rear fork arms, oh and drop links and tightened sway bar... I am now starting to think something with CV has it really sounds like its coming from that area? If it is the CV area what could it be and what would the fix be?

You must be joking. That noise is surely not coming from your car. There is a marching band somewhere in the back ground. I can hear the drummer haha. Don't drive that car any more. Get it into a Porsche Garage. Stop asking silly questions. The next thing to happen will be the engine will explode.

Well I put it on my 2 poster ramp and the only similar clicking I find is when you turn the rear wheel and you can exaggerate the movement to make it click..

I'm reluctant to encourage you from seeking a pro's diagnosis and I would certainly agree with Hurdigurdiman and avoid driving the car/running the engine, but with the car in the air can you grasp the halfshaft and move it about? Try both sides. Be careful. I suspect one is so loose you'll pull it out onto your head. Really, flat bed the car a proper shop for a pro's diagnosis.

Sounds like suspension related clunk or a bad sway bar end link or a loose motor mount. Does it also happen when you go over the bumps? Does it happen at constant speed or only when you apply/disengage throttle at low speed and go over the bumps? When sway bar end links go on Acuras (they do it often) they make exactly the same noise as you posted. When pulling away from the stop at moderate throttle and when going over bumps they make a "clunk".

No noises when taking bumps. Not at a constant speed, doesn't happen at above about 40 mph either regardless of throttle on or off. Butit happens at low speeds with throttle on or off. It also happens if I come to an agressive stop and the transmission downshifts from 4-3 it will make the clunk. But it is definitely related to applying/disengaging throttle. I can control the clunk whenever I feel like. I've gone over the suspension with a prybar , checked everything bolt back there and it all just adds up. On top of the stuff I've replaced also.

Can the inner CV bolts be loose?

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Hmm, if it just happening at low speed during throttle on/off conditions it seems like something is loose and is moving along with engine. Throttle application at low speed and aggressive stops will flex the engine and transmission on the mounts. Try torque braking the car in first gear (Gas and Brake together when stationary) and see if this produces the "clunk". Brake torquing will flex the engine/tranny on the mounts and pre-load the suspension. Do it a few times, have the car stationary and put it in the first gear manually. With foot hard on the brake, push the gas quickly up to 1.5-2k RPM. If it produces the clunk, then have someone help listen to locate the exact source.

Tried that and it didn't produce any clunk. It's only on slow speeds it's doing it. I will make a video tomorrow of the car in the air and I'll show the noise I can make by spinning the rear wheels .

worn Diff? Get it into the garage. They will find it.

Well I was less lazy this time well I think I have found the issue: You Tube Hmph, assuming it's a bearing but I am struggling to find this area on the parts catalogue PDF. Anyone can point me to the area with a PN?

Assuming you are talking about a 996 C4: Could be Cardan shaft Flex Disk . Porsche will sell you a new one for ~$800? or Driveshaft flex disc - C4 and Turbo These folks list the OEM Porsche replacement for $85 KO Performance in Florida http://www.koperformance.com/ Part #: 102539005-57 KO Price: $84.61 Shipping: $0.00 - FREE Shipping! - & *Ship Group Stock Status: In Stock - Ready to Ship! ---------------------------------------------------------------------------------------- Book #: 10 2539 005 Description: Driveshaft Flex Disc Applications: Carrera 4 99 thru 05 Manufacturer: O.E.M. __________________

Sorry mate its a C2 Tip Here is a clearer image of the issue shaft

I don't think there is a flex disk on that shaft. That looks more like it would be a bearing.

Nope no flex disc there. Just having issues finding it on the parts catalogue.

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Howdy.. Is it Part# 99642102001 ?

Nope is a C2. Thanks to Loren I found the area.

I am now suspicious that I have the Pinion bearing whine issue. I do get a whine on the motorway but what isn't explained is this axle play I get on that bearing https://rennlist.com/forums/996-foru...read-this.html

I would suggest have a qualified transmission shop look at this. Clunking noises are not a sign of a worn bearing and just because the noise seemes to come from a certain spot, doesn't mean it actually does. The alumimium case of the transmission can easily distribute any noise anywhere. Some freeplay in the transmissiom is normal too, if you don't know what you are looking for, you can easily mistake them for failed parts. They you start throwing parts at it and it will get really expensive very fast. Have someone that knows more diagnose this for you.

Well I am stuck. Mechanic pin pointed the issue exactly to the spot on the picture. Whining and clunking there. 2 tranny rebuilders said the same but said parts are an issue. Diff rebuilder said the same and didn't want to get involved after seeing parts diagram. No one is willing to take on my car and just say get a new tranny This is the problem You Tube Issue is right in here : Am thinking about just dropping it, tearing the back off and see what is what.

Do you know what to look for?

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That is not differential area, and there is no differential fluid there. Arrows point to where differential is located and to where diff fluid is. If there are no drivability symptoms and all you get is clunk, drive it as is. Since they are offering you to replace the tranny, what do you lose?

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Hoping for a tapered bearing or something bearing like that I can get to fix it! Can't stand to lose anything if the end result is going to be a rebuild or a 2nd hand unit going in

You can easily damage or destroy something that isn't part of a rebuild and then you have a useless core. As I said before, you need to know what to look for when you take it apart and I'm not convinced you have that.

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I don't think the rebuild is in the future, hence he might as well drive it until it stops. If his mechanic wanted to take the job, he would drop the tranny right now and open up the area in question to check for the bearing or gears that make noise. Clearly that is not the case. You can get a used C2 tip for under $3k, and put it in as the whole. Keep the other tip for spares, as transmission itself is not a problem. The bearings/gears that transfer the power to the differential are the culprit here. This transmission is backwards in the 996, hence the need for the extra gears and shaft to transfer the power back to the wheels. The problem in the OP's car is where the output shaft from the transmission meets with the shaft that transfers the power to the differential. The OP's problem lies in the gears in the picture below. They link the transmission output shaft to the shaft driving the wheels. This is comparable picture, but gives you the idea of where the problem is coming from.

I have several of these transaxles, both C2 and C4 if you need one. I have a C4 unit with 40K miles, its not even dirty.

Oh wow, Flat6 is coming to the rescue people!!!!

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Now that gives me a very clear idea. I do have some contacts for a company that manufacturers custom pinion gears! Worst worst worst case scenario I am sure we can do something there! OH man that picture really clears it up from a computer !!!!!

Unless your current tranny is deemed not rebuildable you are generally better off rebuiding the tranny that came of out the car. You know you have not abused the thing. A rebuilt tranny you have no way of knowing what condition it as in. Every part that is replaced affects the rebuilder's bottom line so there is a tendency to reuse parts that should not be reused. Also, in some cases the transmissions are torn down and the "reusable" parts binned then the transmissions are reassembled from the binned parts. The same reusable parts do not always get back into the tranny they came out of. Thus this can lead to increased wear and an early failure, though probably not within the warranty period... The tranny is a ZF and ZF transmissions are common. In most major metro centers there are a number of good ZF tranny shops. Visit your local Porshce, M-B, BMW, VW dealers to find out where they send their autos for rebuilding.

Hi, This is not a typical tranny issue. If it was a clutch pack failure or a valve body issue or a TC issue, it would have been sorted out ages ago as that part of it is just run of the mill stuff!

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Except those are not pinion gears. Custom made pinion or any gear will cost more than an entire used transmission. My father has a gear cutting shop, custom gears are very expensive.

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Some people have all the luck. Nice. I visited one in Redwood City to have a bronze metric worm gear hobbed. It was for my imported lathe. I made the blank and just had the teeth cut. Got a tour. Nice. Went to school and one semester spent it studying large machine tools at GE Westinghouse facility in Sunnyvale. Among other things they had a huge gear hob about the size of a two story house. Used to cut the gears used for gear reduction gearboxes in large ships. To get the gear on/off the machine the roof would come off and then a large overhead bridge crane would used to move the gear in or out. The roof would be put on and the room brought to the right temperature. The gear hob ran day and night non-stop until the gear was finished.