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Glad to see some real tech-types are finally sinking their teeth into the 958 world. The issue with having any newer car is that everyone seems to think "take it to the dealership" is the answer.
That being said mine is there getting the variocam bolt recall done right now
I also want to share that the "crunching acorns" noise making slow speed left-hand turns or when pulling away from a stop and turning can be the PTV+ diff if you have one. Mine was doing this and I pulled fuses (2 and 3 on the dash right hand side? 3 and 4? check your diagram of course) for PTV+ and while I did get a "rear locking diff fault," it completely eliminated these noises. They returned when the fuses were reinstalled. So, in my case it was just the PTV+ diff locking a little more than it should at low speeds and the resulting mild binding of the rear axles because of it.
My point being that people love to blame everything on the TC when it isn't always the case.
i've got the PTV+ diff but no shuddering so to speak, just the straight line hesitation. I'll try your trick though, thanks for the option!
We've had a few days with 70+ degrees so the windows and pano roof have been opened.....and noticed last night some clicking while maneuvering into my parking spot in the garage.
I've got an extra bottle of Ravenol so will put it in tomorrow for S&G's just to see if it reduces any symptoms. My "old" fluid is only 6 months old, curious to see what it looks like now.
I tried to find a part number on the outside of my transfer case but couldn't find anything. Where is it? On the top?
Did a fluid change after 3,000 miles and roughly 4 months. You can see how black the fluid was and the surprise I found stuck in the drain plug hole. I believe its part of a friction disk.
shifts smoother but still has some funky tendencies.
That doesn't look good. Wonder how it got out of the clutch pack? The pack is pretty much contained in the outside basket. I think the PN is on a paper tag.. which obviously is going to disappear sooner or later.
Apparently the fluid is what fails, which then leads to failed hardware like the TC clutch packs, etc. I just posted the following in the transfer case sticky thread....
Yesterday I was at one of two P dealers local to me that I do business with. While checking out some new rides, my salesman introduced me to one of their more senior technicians that happened to be in the sales area at the time.
In chatting with him about a number of things, we got on the subject of the 958 transfer cases. He mentioned the latest revision of the case (which we've discussed in this thread) and the associated new hardware like the vent kit, etc.
According to him, the issue has always been a contamination of the fluid. The total amount of fluid the TC holds is very little actually (1 liter or so?), so any small amount of contamination can have significant impact, and that impact specifically degrades the friction modifiers in the fluid which is at the root of the problem. In some cases a fluid change corrects the issue (which we've seen evidence of), and then in other instances the damage caused by the fluid contamination is more severe and thus permanent, requiring a TC replacement. He mentioned that the vent kit helps reduce fluid contamination, but it is recommended now that the fluid in those transfer cases (even the new design) be replaced every 20k miles.
New parts from AWD.tech came today. After looking at the new bits, I can pretty much guarantee that one or more friction discs are coming apart.
I've done a lot of stuff but this may turn out to actually be one of the most satisfying automotive tasks I've done since swapping an ///M3 motor into my e30.
New parts from AWD.tech came today. After looking at the new bits, I can pretty much guarantee that one or more friction discs are coming apart.
I've done a lot of stuff but this may turn out to actually be one of the most satisfying automotive tasks I've done since swapping an ///M3 motor into my e30.
Great start! Pictures, pictures, pictures.. BTW - can you give us a view of the plain steel plates? I'm curious how they lock into the clutch basket to transfer torque.. and will be very curious to see if there is any notching of the grooves in the basket when you disassemble them. That was the biggest cause of problem wet multiplate clutches on motorcycles.. once the groove gets notched the plain steel plates don't clamp smoothly.. and the driven plates (the ones with friction material on them) - would start to slip a bit - heating things up and eventually have the friction material wear out or flake off..
Any idea on what the torque settings for the various components you'll be R&R'ing are? Usually if I can't find that info for the specific part, I'll look for standard torque settings for each size/type bolt (Google helps.. there are tables of this info..) and just tighten to 80% of that value. Some older service manuals used to have those tables.. and only listed torque settings for things like head-bolts, etc.
I also want to share that the "crunching acorns" noise making slow speed left-hand turns or when pulling away from a stop and turning can be the PTV+ diff if you have one. Mine was doing this and I pulled fuses (2 and 3 on the dash right hand side? 3 and 4? check your diagram of course) for PTV+ and while I did get a "rear locking diff fault," it completely eliminated these noises. They returned when the fuses were reinstalled. So, in my case it was just the PTV+ diff locking a little more than it should at low speeds and the resulting mild binding of the rear axles because of it.
My point being that people love to blame everything on the TC when it isn't always the case.
Very true. I recently mentioned elsewhere in this forum that when my '11 CTT was at the dealer earlier this month to have the AH08 recall done, I also had them replace the fluid in the PTV+ rear diff.
I have the latest version of the TC and associated parts (new vent tube kit, etc.) and that certainly took care of the 'stuttering' experienced during straight line acceleration. But at times the 'crunching/jerking' in tight slow speed left hand turns still occurred after the TC replacement. The PTV+ rear diff fluid change took care of that completely. Porsche tech recommended that the TC fluid and the PTV+ diff fluid be replaced every 20k miles or so, despite what the official maintenance schedule calls for, using the proper OEM Porsche fluids. Worked like a charm on my vehicle.
Great start! Pictures, pictures, pictures.. BTW - can you give us a view of the plain steel plates? I'm curious how they lock into the clutch basket to transfer torque.. and will be very curious to see if there is any notching of the grooves in the basket when you disassemble them. That was the biggest cause of problem wet multiplate clutches on motorcycles.. once the groove gets notched the plain steel plates don't clamp smoothly.. and the driven plates (the ones with friction material on them) - would start to slip a bit - heating things up and eventually have the friction material wear out or flake off..
Any idea on what the torque settings for the various components you'll be R&R'ing are? Usually if I can't find that info for the specific part, I'll look for standard torque settings for each size/type bolt (Google helps.. there are tables of this info..) and just tighten to 80% of that value. Some older service manuals used to have those tables.. and only listed torque settings for things like head-bolts, etc.
The new steel plates? I will get some pictures for you and post them up in this thread if that's what you want to see? If you want to see the old ones, i'll post those in a few weeks.
I haven't found any torque specs. BMW has an extremely similar case that uses the same components so I will use that as a guide....as well as bolt size info from the web. I have a calibrated torque wrench that I can use so thinking I could try a handful of the bolts and work up to a torque where the bolt will actually move. I'm leaning more towards the last option.
I wonder if software calibration will be required. I was at the stealership yesterday and service manager told me that a TC replacement requires some software adaptation done. Supposedly you need to 'program in' the electronics inside the TC to match the car. Not sure if that is the usual Porsche BS or not.
I wonder if software calibration will be required. I was at the stealership yesterday and service manager told me that a TC replacement requires some software adaptation done. Supposedly you need to 'program in' the electronics inside the TC to match the car. Not sure if that is the usual Porsche BS or not.
BLUF - Bottom line up front, I suspect the systems onboard that tell the "dumb" transfer case control unit when to activate, need to know the starting state of the transfer case and last lube oil change. Having had the PTM perform well multiple times, it would not surprise me if there is an adaptation phase.
When I read the 2011 Service Information Technik Introduction, and review its high level drawings/artwork, there are no electronics inside the transfer case. There is a control unit that is attached to the transfer case. Per page 106, "PTM function. The control unit (4) calculates a standard torque split using different pieces of input information.Depending on the nature of this information, the servo motor is activated and a worm drive (3) then turns the ball ramp (2), which pushes against the multiple-disc clutch (8)."
Also, per page 108, "Maintenance calculator. The all-wheel control unit is equipped with an internal maintenance calculator. Calculations are made using wear integrators:
• Chain load
• Multiple-disc clutch load
• Distance since last oil change
• Counter indicating how frequently the clutch was closed almost 100%
If the calculated value exceeds the diagnostic threshold of 145 kWh a corresponding entry is made in the fault memory. This value must be read out during maintenance using the PIWIS Tester and the oil changed if necessary. The process is menu-guided in the PIWIS Tester."
Lastly, from page 105, and why I suspect that the systems supporting PTM needs as much info as reasonably possibly: "PTM comprises the following systems:
• Active all-wheel drive with electronically and map-controlled multiple-disc clutch
• Automatic Brake Differential (ABD)
• Anti-slip regulation (ASR)
The PTM on the Cayenne, Cayenne S and Cayenne Turbo is designed as an active all-wheel drive (hang-on all-wheel drive). The system is characterised by a compact overall design.
The multiple-disc clutch installed in the PTM transfer case is controlled by an electric motor and regulates the distribution of drive power between the full-time drive rear axle and the front axle in a way that is fully variable without a fixed basic distribution. The vehicle permanently monitors the driving state and can thus react to different driving situations and driver requests (e.g. accelerator pedal’s position, steering wheel angle or PSM switch positions, Sport button, etc.). This allows the installation of additional software that is designed for the driving dynamics of the hang-on all-wheel drive and enables the vehicle to react to certain situations and even prevent undesired slip on an axle before it occurs. However, the software can only be installed if a hang-on all-wheel system is integrated in the other chassis systems. Sensors continuously monitor various parameters, including the speeds of all four wheels, axial and lateral acceleration of the vehicle and the steering angle. If the rear wheel spins during acceleration, for example, additional drive power (if necessary up to 100% more) is distributed forward through greater intervention of the multiple-disc clutch. The all-wheel drive is therefore fully variable.
The distribution of the drive torque across the front and rear axles depends on a number of factors such as speed, acceleration, the selection of Normal or Sport as well as the selected PSM mode, etc. In order to achieve good traction when driving off or accelerating, the front axle torques tend to be higher in these situations than when the vehicle travels constantly in a straight line. The vehicle reacts to a consistent driving style by reducing the drive torque on the front axis to minimize friction losses, for example."
02-18-2018, 01:54 AM
