Originally Posted by deilenberger

A strong recommendation to anyone with a Cayenne:

Make a transfer-case (TC) oil change a regular maintenance item. I'd suggest every 30,000 miles, and checking the oil every oil change when the car is up on the lift.

Doing a TC oil change on a lift will add about 10 minutes to the time spent changing the engine oil. Perhaps less. The TC drain and fill plugs are RIGHT THERE IN YOUR FACE - you actually could touch both of them with your nose if you were so inclined. Nothing in the way, lots of access, nothing has to be removed. I'll add a photo taken from underneath when I have a chance.. but there is no reason to not change the oil.

So far - over on RennTech - we have 4 people who were experiencing TC symptoms - told by Porsche they needed new TC's - who have changed their oil and no longer are experiencing ANY symptoms. We have one person who changed their TC oil and his symptoms were reduced but not eliminated - but - he didn't use a recommended oil, or even an oil that the oil manufacturer suggested for the use. He is going to change it again using one of the recommended oils.

My own experience: My '11 Twin-Turbo didn't exhibit the symptoms other people had. The common symptom is a roughness in accelerating and some popping/clicking noises from under the car. Mine had a tiny bit of unevenness on acceleration - but not so much that I thought it abnormal. I have 72,300 miles on the CTT.

I changed the oil today - putting in the new part# Porsche oil. It was available from SunsetPorscheParts.com - they had the best price (around $45 + shipping.) Local dealer wanted $75 for it.

I did it on a lift since I have a friendly independent who was interested. It took longer to set the lift up to lift the Cayenne then it did to change the oil.

What drained out was black. It had a slight burned odor to it, but not really strong. It didn't smell like gear oil, or the oil that was going in. It seemed rather thin. There was no sign of water contamination. I've saved a sample to send to Blackstone to analyze.

As to what causes the oil breakdown - I suspect several items: One is heat. There is a small deflector right under the TC that is there to direct air up over the case and cool it. There has to be a reason for that deflector. I wonder if failures happen more often in warmer climates? The other may simply be use. The design is such that the clutch is ALWAYS partly engaged - and always slipping. That's how power is transferred from the rear to the front or rear to front. If someone drives in situations where they do a lot of turning - that will cause more slippage of the clutch as the ratio of front/rear torque changes. If someone has partly worn tires on one axle - that will cause continual slippage as the system adjusts the difference in rotation speed of the tires. ALL of these situations do two things - wear the clutch - and heat up the transfer case. Excessive heat is certainly indicated on TC's where people have reported a burned smell in the old oil.

The new oil had the usual gear-oil sort of smell (sulphur) and was a light golden color. Took about 2 minutes to pump it full and button it up.

This could EASILY be done on one with air-suspension by simply going to the highest suspension position and sliding under the vehicle on a piece of cardboard.

The result surprised me. It felt different backing out of his parking lot. After about 2 miles it felt much different. The acceleration is absolutely smooth now. It sort of encourages me to put my foot in the pedal..

So - why is this?

I believe the oil has broken down due to heat, and is contaminated with clutch wear particles. The clutch in the TC is a multiplate wet clutch. That means that the oil used IS important for smooth operation. Oil that is too thin and contaminated with wear particles will cause uneven clutch operation.

It's my belief that the roughness in acceleration (and on turning) and the noise are symptoms of the clutch plates engaging erratically, sticking and then releasing.

New oil seems to cure this - at least in the vehicles it's been tried in. People have gotten success using other than the expensive Porsche oil. An oil from Ravenol has been used successfully - and claims to meet the Porsche specification for the oil.

Car manufacturers like extended service intervals.. for a simple reason, it makes it easier to sell cars. People are afraid of high maintenance costs, (which would be very true if this was done by Porsche - the estimate to change the oil was over $200..) so the manufacturer extends the service intervals as far as they possibly can and have the car survive the original warranty period and any CPO period they might have to cover. At 100,000 miles - to the manufacturer - the car is basically dead to them. They have no continuing interest since they aren't going to make money off it.

So - it's easy and inexpensive to do - and it has FIXED issues that Porsche dealers wanted $4,000 to fix.

Just do it. Change your TC oil. And to check the oil at oil change intervals - remove the top fill plug and stick your finger in (or if it's full and warm some oil will run out) if the oil is DARK - replace it.

YMMV - but bet not a whole lot..

Looking forward from under the car:

Originally Posted by CayennedieselV8S

Hi folks,

New to the forum and just purchased, as per my screen name, a 2015 Cayenne 4.2 V8 Diesel S (on 38k miles)
Just looking for some definitive guidance on the TC issue, as to what models are affected, as i have read conflicting opinions on other forums.

I read online that the TC issue is only a gasoline version issue and not present in the diesel versions, but i have also read that it is common amongst most models in the 958 range?
Most of the issues i've read about so far seem to be on earlier models, does anyone know if Porsche changed the breather design or changed the inspection / service schedule on the fluids on later models?

We will take delivery of the car on Jan 31st, so still have some time to get the dealer to at least check / replace the fluid as i'm sure they done want a warranty claim either!
There were no obvious noises during the test drive, but knowing my luck it will happen a week after i take delivery!

Many Thanks
Neil

Originally Posted by Porsche_1988

Is it state specific? I did not get it and am original owner.

Originally Posted by steph280

Those of you that changed the TC fluid, did the problem every come back? If so, how long/miles did it last?

I changed my fluid 4 years and 25K miles ago, symptoms still hasn't come back. I am actually wanting it to come back so I can get it replaced under the recall campaign. Right now they wouldn't do it since they couldn't duplicate the problem.

Originally Posted by steph280

Those of you that changed the TC fluid, did the problem every come back? If so, how long/miles did it last?

I changed my fluid 4 years and 25K miles ago, symptoms still hasn't come back. I am actually wanting it to come back so I can get it replaced under the recall campaign. Right now they wouldn't do it since they couldn't duplicate the problem.