Prairiedawg

Ahh, ok. Pwm is a little over my head. I kind of understand it but never deal with it so I never learned about it. My understanding is, it pulses signals of different lengths for a feedback loop. Still learning I guess. Thanks for all you guys are doing, keep up the good work.

12gauge

Sure, I'll get by with what I have, but why, oh, why has Porsche conspired to block me at every turn? Come on now, it's not that bad, I say to myself as my OCD screams at the top of its lungs.

I performed what feels like an exhaustive search throughout the various models and years within the Porsche Parts Catalogs for the RIBE AL9 Oval Head M8x50 screws gearcase fasteners. Why you ask am I tilting at this windmill? Because I found what I believe to be the proper torque value and subsequent angle for these aluminum screws and the Porsche (of course) documentation recommended replacing them with new. They call out the torque-angle method to achieve the highest tensile clamping force on most every aluminum screw, in this case is torque to 10NM, then follow up with rotating the fastener 90 degrees. So, I've gone on a quest not believing that the factory designers, the 2nd party transmission designers and the 3rd party fastener manufacturer ALL would only use those particular fasteners on my transmission and nowhere else ever, so help them god. Here's what I found anyway.

I found M8x55 oval head AL9 screws used on the front engine cover on Panamera front engine covers. Hot Dog! On my gearcase all but two threaded holes are thru-holes so I'll just nip off 5mm on those two and I'm golden. Feeling cautiously optimist of my find, the dealership parts guy (great folks, really) says, "yeah I've got some of those in stock, want them?" The two illustrations below are what I found:

Scoured the Porsche Parts Catalogs and found this M8 aluminum oval head screw used on a Panamera front engine cover. My PDK gearcase uses M8x50's. These screw heads are approximately 0.75 to 1mm less material between the socket well and the threaded shank.

The end of M8x55 oval head screw (p/n: 999-073-913-31) has this weird dog point for the additional 5mm length.
Alrighty then.

Kuro Neko

Buried above is an observation my shop made - they appeared to be the same as a Benz fastener.
They work on both Benz and Porsche, had them on hand, and used them accordingly...

mabdu007

Got a used TCU off ebay. Programmed it. P1872 gone, now the p0841 code is showing up and it's the only fault code. So transmission oil pressure. But now I'm worried about a leak. I noticed every now and then when I start the car to work on it a little oil drops to the garage floor. I tried finding the source and it seems to be coming from the bell housing (little hole at the bottom). My pressure sensor 1, which is the one throwing the code, reads around 1.1 bar in terms of pressure.

My question is, how low is this pressure? Or is this roughly close to normal. And if it truly is trans oil dripping from bell housing I'm guessing that means radial shaft seal or clutch cover o ring is bad.
The oil isnt pouring out and last I checked level was fine. Could this leak lead to a low pressure reading which would lock the transmission from moving?
Any insight is appreciated!

jjrichar

I think you are correct in your assessment that the oil from that hole is a leak from the radial shaft seal or clutch cover O ring. Or it could be from the rear of the engine.

Could this be the cause of the low pressure signal? I don't think so, as the pressure measured is for clutch 1, which is buried well behind either of those places that might be leaking. 1.1 bar is about 15 psi. This is peanuts compared to the clutch pressure you would expect when that clutch is fully clamped. I'd be expecting at least 10 times that. If this is the pressure you are seeing for clutch 1 pressure when you in reverse or an odd numbered gear, there is clearly an issue somewhere. The pressure for this when in an even gear should be close to zero.

What? Maybe it's a failed pressure sensor. Or EDS 1 (valve body solenoid) has failed. I don't know how exactly to test the pressure sensor, but the solenoid resistance can be checked. This isn't definitive, but if the resistance is incorrect (should be about 5 ohm), this may guide you. Both pressure sensor and solenoid can be checked at the TCU.

mabdu007

Hello,
​​​​​​@jjrichar thank you for your input! So I wanted to reply and add more information, I realized I barely put any info.
Background is I have a 2012 Panamera S. Doesnt drive, and is in limp mode. No gear engagement. Initially I thought TCU because it kept throwing communication errors, granted once I swapped in a used TCU and programmed it I no longer get these. However, the P0841 code that was stored as a permanent fault in my last TCU is back. And just to be clear pressure sensor 2 also reads around 1.2 bar, so I'm not sure why that one isn't throwing any codes.
When I look at signals from pdk it says clutch is open, presumably this could also he why pressures are low correct?
The only other values that stand out to me is input to speed sensor 1 is 0 while sensor 2 is close to engine's rpm. Also as @PV997 pointed out the output for pressure regulator 7 is also 0 despite receiving signal, and I'm not sure if this is normal for a RWD.
I ordered a distance sensor because at one point during diagnosis I had a random set of codes thrown for shift rods, although strangely enough these haven't come back. Admittedly I stupidly ordered a part just to throw at it out of frustration lol. Once I put the part in I can't return it. So I was hoping there was something else I can try before committing to it.
Is there anything else I can try or any other information I can strip chart that would help? One thing to note I haven't performed the pdk calibration just yet. Would that be the next step?

I'm at a loss at the moment. Any and all help is very much appreciated. Thank you all for the dedication and information.

12gauge

Thanks, Black Cat for responding! I performed searches and didn't find the reference in this thread, but Vlad at T-Design told me about a customer in Japan that mentioned his mechanic's reference of a MB 722.9 transmission, so assuming it was you, I went down that rabbit hole. The only M8 screws I could find were for the torque converter housing (MB p/n: 0049902312) and readily available in the States, but they are M8x45mm Oval Head Screws... 5mm short. The removed PDK gearcase half has a 30mm boss thickness which allows 20mm of the original ZF provided M8x50 AL9 oval head screw to thread into the other half of the gearcase. So my quest continues until I come time to reassemble, then my compromises will come to realization.

...when you come to a fork in the road, take it...

12gauge

My 2012 Cayman [987.2] has a slotted bearing retainer nut captivating the lower shaft bearing onto a shoulder on that shaft. The nut is curious to me in two ways; first it's a staked nut meaning it has a thin extended rim that once torqued was crimped 180 degrees out into notches cut into the first three threads of the shaft. The staking tool ZF used was perfect for the job in every way, of course. In that it neatly sheared the staking rim and very tightly compressed the formed tabs into the notches of the shaft end.

Normally, a staked nut is to be replaced so one doesn't take any great care to lift the crimped section before unscrewing it, as it will be replaced with new upon reassembly. But in this case considering the maniacal designers of this transmission, I hand ground a narrow wedge-like chisel just wide enough and narrow enough (so I thought) to get under these staked tabs and lift them steadily up and out and above the threads. But the fairly mild steel and thin cross section of the tabs began to give way causing me to fear chiseling the tab right off, so I stopped while the rear portion of the tab was still in the slot to some degree. The nut loosened fairly easily after the tabs were lifted.

However, I didn't know then what I know now or maybe I would have taken more time or changed shape of my hand ground chisel edge to lift the rest of the tab above the thread crests. Upon unthreading the nut, it seems that I have created striations in the tabs by the shaft's threads causing me angst that I might break the tabs while bending them back in the slots, once the nut is run back on and torqued. They are certainly weakened in any case, and one tab is now slightly shorter from the exercise. Bummer.

I have been considering some remedies since I can't find this M33-1.5 slotted bearing retainer nut with a staking rim anywhere:

• Find a replacement nut - anyone? anyone?
• Add a hardened washer or turn the nut face down just enough to have it clock on a new portion of the staking rim
• Stop driving myself crazy with this minutia and use the existing tabs however compromised

Love to hear anyone's thoughts from those who have removed these nuts before; methods, retightening, replacement, etc. or seen it done.


Axial view of bearing retainer nut beautifully staked in two places. Obviously, ZF has zee special staking tool for such clean shear lines and tightly bent tabs


I made a special chisel to narrowly fit the width of the tab and wedge under it with light taps... but alas, I broke one partially off and scored both on the shaft threads. Bummer.

jjrichar

Now your pictures above of the tools used make sense. I had no idea this was how it was for the earlier transmissions and since they had moved to circlips. Really nice to know.

As to your question, I'd be doing my best to crimp with what you have but also use some red loctite to ensure it can't move. It would be pretty simple to remove the rear plugs at some stage later to visually check the nut isn't backing off.

jjrichar

I didn't realise the transmission was from a Panamera. Whilst I don't think ZF would have fully reinvented the wheel when making your transmission, I really have no clue about it. My knowledge is very much what is happening mechanically within the sports car transmission. My diagnostic knowledge is low, and so I don't think I'm going to be able to offer you much help.

Note that clutch pressure is only going to be applied (and seen by the pressure sensor) when the clutch is activated. ie when the car is moving. Otherwise it should remain at approx 1 bar, which is atmospheric pressure. If however it's giving a pressure sensor fault that is generally a good starting point at where the failure is.

EDS 7 is for a limited slip diff in the sports cars. Does your car have this? If not I'd disregard.

Regarding the speed sensor, I wouldn't read too much into that. What are the distance sensors reading? Are all close to zero or is one reading a distance. Normally in park the transmission selects 1st gear. So with no clutches activated, this stops shaft 1 from turning, but shaft 2 is able to turn as it's not locked because no gear is engaged. The clutch disks are still very close to each other and there is friction, which will make the shaft turn if no gear is engaged.

Definitely do a cal. In all the Porsche troubleshooting docs I have the first thing they say to do in most cases is a cal.

mabdu007

So got home and tried to mess with the car a bit. When I put car in gear the pressure goes up to 1.8 bar, but then I saw a stream of trans oil come out of the bell housing. Pressure never went past 1.8 bar. Once I put it back into park the oil stopped spilling out.
What I'm thinking now is when the system tries to pressurize to engage 1st gear but the pressure is causing fluid to leak out and hence no shifting. But I'll admit I'm still learning and don't know if this is a reasonable conclusion. The only fault code the piwis gives me is that pressure sensor still.
I'm wondering if stop leak has any role here.

mabdu007

The travel sensor 3 reads 9.4, the other 3 are around 0.5.

And I gotcha, I'm starting to understand a little. Perhaps it really is a faulty sensor. I'm just at a loss as to how much this leak is affecting the lack of gear engagement. My ignorance is nagging that there is involvement but I'll admit I have no clue.

jjrichar

Travel sensor reading 9.4 and the others close to zero is good. That's what it should be in park.

If there is a big leak, there is a non-electrical problem, and I'm expecting it's to do with clutch 1, as you are getting the pressure error for this clutch, and it's leaking hard when you select this gear. I'm surprised it's leaking from that hole though. When full pump pressure is applied to the clutch it is always going to hold the fluid within the transmission. If it's coming out that is some sort of seal issue.

Note that when you select a gear and the car isn't moving, zero pressure is being applied to the clutch. Both pressure sensors should be about 1 Bar. On my project car it's 1.1 and 1.2 Bar for the two sensors when not moving. It's only when you take your foot off the brake and it says it's time to move that it will begin to slowly apply pressure to clutch 1 to begin moving. This pressure will increase all the way to the point where it's fully clamped and then full pump pressure will be applied.

From the symptoms you have given my solution would be to remove the transmission from the car and then the clutch pack. I'm expecting there is a seal there somewhere that needs replacing. It might be within the clutch pack itself if there isn't anything obvious. Thinking about it, if there is a leak in one of the clutch 1 piston seals (inside the clutch pack) the flow of oil that would come out sideways from the clutch pack might be such that it is forces past the large o ring around the front plate and into the bell housing.

This is just my best guess from my knowledge of the sports car transmission.

mabdu007

That finally makes sense. I think I'm understanding a lot better. So readings are fine I guess, which I guess means it has to be simply a pressure sensor.
Do you think it's worth it to open the pan, swap the sensors, and see if it starts throwing pressure 2 sensors before I try to drop the gearbox?

My problem now is after I tried to calibrage I get torque intervention not possible and some codes relating to hydraulics - one of which says gear 2 disengagement block.
weird thing is I changed the valve body already, it was a used one so maybe it was bad from the get go?

jjrichar

Here's where my lack of knowledge of your transmission shows itself. Where are the pressure sensors? On the VB? In the sports car transmission they are behind the clutch pack.
Regardless, it shouldn't be leaking. No electrical problem from what I know should ever have oil come out of the bell housing. Again, this is just speculation on my part.