When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have a 2003 Cayenne Turbo and I have jerky transmission! I realise that this sounds like the classic valve body issue but it isn't. Here's what's going on...
The car shifts gears smoothly when cold. No problems at all. But, there's a jolt when I thought the car changed from 2nd to 3rd as it starts to warm up. It's subtle at first but gets really noticeable when the car is fully up to temperature. I do a lot of city driving at the moment so there car is always changing from 2nd to 3rd, making the problem really annoying.
I've replaced the transfer case oil and had the valve body replaced but still have the same problem.
I put the car into manual and it jolts, even if I don't change from 2nd to 3rd! This happens every time at 20mph. This is the point where it would change from 2nd to 3rd in auto. So not a gear change issue after all.
I was told that the new valve body could take up to 1000 miles to smooth out problems. Not sure how true this is as the problem feels identical to before the valve body change.
I turned off PSM (leaving the car in auto) and the problem seems to go away? Is this because it's much higher revving when it passes 20mph?
Apologies for yet another transmission post but I can't find the answer to this anywhere. I've just taken it to a local Porsche garage but they can't find the issue. They started talking about the transfer case...
I've just seen a youtube video saying it's worth changing the transfer case fluid several times (rather than just once). I'm looking at every possible fix other than a transfer case repair.
So turning off the PSM fixes the problem? I would look into the transfer case motor. That guy controls the front/rear torque split, and does some witchcraft at various speeds to change f/r bias. I don't know if this is your problem, but that would be my best guess. I've seen threads around here on the subject with people changing t-case control modules and/or the t-case motor on earlier cars, which your beta version 2003 most certainly is
Hope this helps!
Thanks Slavie, I'll look into that. I'm not 100% turning off PSM solves the problem. But it does make it much less noticeable.
It's not too bad if you're very gentle with the accelerator when pulling away from the line. There's a real jolt if you're giving it the beans. The problem is at the same point every time (approx 20mph). I wonder if a valve is opening or a clutch is engaging at that speed whether you're changing gear or not.
Just been looking at the prices of after market TC motor and module. They're not to bad so I'll order them in the hope it fixes the problem.
What nobody tells you about a VB change is that when they dyno the new VB before it is sent to you it is based on the specs of a new trans. Even resetting the adaptations can only compensate so much with the re-learning. Sometimes the solenoids themselves need to be adjusted and I have found that this can make a huge impact. A failing VB has a tendency to ruin a perfectly good transmission if allowed to go on too long. The TC motor usually either works or it doesn't and can be intermittent, but almost always a fault is generated.
TC chains do wear out and when this happens you will get a clunk when on and off the gas and even binding. The need to change the TC CU when updating the stepper motor is a myth. The updated software was an attempt to correct the symptoms without actually having to replace the motor. VW AG still does this to this day across many platforms/ systems.
What nobody tells you about a VB change is that when they dyno the new VB before it is sent to you it is based on the specs of a new trans. Even resetting the adaptations can only compensate so much with the re-learning. Sometimes the solenoids themselves need to be adjusted and I have found that this can make a huge impact. A failing VB has a tendency to ruin a perfectly good transmission if allowed to go on too long. The TC motor usually either works or it doesn't and can be intermittent, but almost always a fault is generated.
TC chains do wear out and when this happens you will get a clunk when on and off the gas and even binding. The need to change the TC CU when updating the stepper motor is a myth. The updated software was an attempt to correct the symptoms without actually having to replace the motor. VW AG still does this to this day across many platforms/ systems.
02-10-2021 | 05:24 AM
Not another jerky transmission thread?!
