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Went up the chain a bit and finally received my service receipt showing the transfer case was replaced and the Cayenne was deemed to be repaired. Also received an apology stating that I was "misinformed" about the rest of the non-existent issues.
I can't say that I've ever really trusted dealerships, but this experience was just next-level bad. I'm sure lots of good service departments exist; however, the one I picked just wasn't one of them. Sad as their store is very modern and they have great inventory.
Went up the chain a bit and finally received my service receipt showing the transfer case was replaced and the Cayenne was deemed to be repaired. Also received an apology stating that I was "misinformed" about the rest of the non-existent issues.
I can't say that I've ever really trusted dealerships, but this experience was just next-level bad. I'm sure lots of good service departments exist; however, the one I picked just wasn't one of them. Sad as their store is very modern and they have great inventory.
Terrible...Don’t fall for it Steve. No such thing as good Porsche dealership. I dont even give them credit for fessing up. Standard operating procedure.
When the car determines that more power must be sent to a different end of the vehicle (say front wheels have traction and rear wheels are slipping) - a stepper motor actuates a ramp type device (rolling ball in a track that changes depth) that changes the pressure on the clutch plates, allowing it to direct more power to the front of the vehicle.
From looking at the mechanism of this TC, it looks like an electrically operated slip clutch that allows slip but locks on command.
Slippage depends on what the traction control unit decides to do.
And with the ball-ramps, increased torque squeezes the plates harder.
But in any case, it wastes power by slippage, which can burn up the oil if slipping too much.
As opposed to a gear mechanism that woudn't 'waste' the power or generate heat.
^^ Here's a diagram of the 955/957 drivetrain. ^^
And here's a cutaway diagram of the 955/957 transfer case.
That 955/957 looks like a locker transfer case.
Does anyone know where there's a similar diagram showing what's inside the 958 transfer case?
Steve, this is all great info............until you tell us what dealership did this ?? we have 1/2 the story.......568.00 for an oil change ??? the dealer in Chandler AZ only charged me 350.00 ..... for turbo S.
And here's a cutaway diagram of the 955/957 transfer case.
That 955/957 looks like a locker transfer case.
Does anyone know where there's a similar diagram showing what's inside the 958 transfer case?
The 958 case is very similar just without the 2-speed planetary gear assembly. They both slip the clutches to change the ratios between front and rear. In the 958 cases - in normal highway cruise conditions, 100% of the power is sent to the rear-drive. Makes it more efficient. In that case, I believe the clutch is freewheeling. The 958 under most conditions feels like a rear-wheel-drive vehicle, and I expect that's because under non-slip conditions - it is. The Japanese like my wife's Lexus RX350 uses a front-wheel-drive assembly with the rear-wheel-drive controlled again by a transfer case, but I know on it - unless a front wheel is slipping under power, the rear is pretty much ignored. The Porsche system allows for nice things like Porsche-Torque-Vectoring and rear-wheel steering.
Thanks for the pics, that helps a lot.
I wasn't aware the 955 / 957 had a 2-speed transfer case? ( a granny? )
Originally Posted by deilenberger
In the 958 cases - in normal highway cruise conditions, 100% of the power is sent to the rear-drive.
So the 958 is a direct-drive rear wheel drive that lets thge front slip?
And with a servo motor, squeezes the clutch discs to throw some power to the front - if the rear wheels slip?
I like the Torsen better, but that's only on the diesel right?
Thanks for the pics, that helps a lot.
I wasn't aware the 955 / 957 had a 2-speed transfer case? ( a granny? )
So the 958 is a direct-drive rear wheel drive that lets thge front slip?
And with a servo motor, locks up the clutches to throw some power to the front - if the rear wheels slip?
The torsen transfer case (on diesel and hybrid) is "reactive" - lockup occurs when slipping occurs. The active clutch transfer case (on base, S, GTS, Turbo) is proactive and locks up to prevent slip from occurring. It's fun to watch it in action if you have the ability to monitor the clutch torque while driving. It's working hard all the time... except when highway cruising under low load.
The active clutch transfer case (on base, S, GTS, Turbo) is proactive and locks up to prevent slip from occurring.
..... It's working hard all the time... except when highway cruising under low load.
So what causes the jerking people feel with transfer case problems?
Is this the front axle clutching in & out?
Where the jerking is "tire slip of 2wd" vs "tire slip of 4wd"?
Based on this understanding:
Cayenne is basically a direct-drive rear-wheel-drive car that has "active front drive assist".
Is this a correct understanding of the Cayenne AWD system? (the active, not the Torsen)
I am trying to understand this problem.
It makes sense that if the clutches were slipping, they could get hot and burn up the oil, contaminate the oil, and wear out the plates too.
But if this is only during max acceleration, when the front drive is making up for rear wheel slip..... that doesn't add up to much.
And there's slip-differentiation when driving curves. But most of that is very low speed maneuvering and very short duration.
I don't see how it would heat up and burn the ATF.
The clutches in the transmission work much harder than this differentiation clutch, which makes a slow, lazy rotation every once in awhile.
If the car is driven hard, that's different.
In that case how can the 440,520HP versions even survive at all if the base model is having trouble.
If it's water intrusion, that will damage parts by rust and by degradation of lubricity.
From this article (Water in Oil Contamination)https://www.machinerylubrication.com...ontaminant-oil For rolling element bearings, the situation is even worse. Not only will water destroy the oil film strength, but both free and emulsified water under the extreme temperatures and pressures generated in the load zone of a rolling element bearing can result in instantaneous flash-vaporization causing erosive wear to occur.
Does anyone understand the problem better and able to explain what's happening in the Transfer Case?
If it's only clutch-wear related, and not any bearing problem or chain problem, I'm puzzled. It kinda sounds more like a control-system problem.
-or more likely,,,,,
That I'm mistaken in my understanding of the drivetrain
(where LOTS of power is going thru this TC clutch at all times)
The torsen transfer case (on diesel and hybrid) is "reactive" - lockup occurs when slipping occurs. The active clutch transfer case (on base, S, GTS, Turbo) is proactive and locks up to prevent slip from occurring. It's fun to watch it in action if you have the ability to monitor the clutch torque while driving. It's working hard all the time... except when highway cruising under low load.
How are you able to monitor this? A friends Macan Turbo has the torque split visible in the digital guage cluster but my 958.1 turbo doesn't. Is this something I can see in Dash Command or something?
for the loose bolts, those are just exhaust hangers, so not a huge deal, but still very sloppy.
When I rebuilt my 60k mile diff, the clutch plates measured nearly identical to the new ones in thickness. There could be some wear in the spring washer stack or some chain stretch.
But there was no real smoking gun for me. Definitely drove better when reinstalled, but I couldn't tell you why.
Scheduled an inspection for December 8th, which is a few days before my 10 year in-service date of 12/13/10.
Not sure what to expect as no significant symptoms since I've been changing the fluid every other oil change for the last 40K miles and now have 120K on it. I did have jerkiness before the initial fluid change but don't know if that will be enough. The SA said they've pretty much just been swapping all of them out but I somehow doubt that.
11-18-2020, 04:28 PM
