offagain

Hi all,

First time poster here - so hi everyone!

I have a 2011 Cayenne S and its great, but it seems to have developed a strange issue with the gearbox! Basically, car is completely cold, so left over night (I am in Northern CA, so its not exactly really cold weather, but you get the idea) and it starts up fine and no issues.

Pull off my drive and its also fine - selects the right gear and no issues. Even changes up and down as I go through the first few turns around the streets where I live. But, if I stop at a set of lights that are within 1/4 a mile, it will usually NOT get the right gear. Car is running fine, but when you go to pull away the revs will rise but the car wont move! Then, after a second or two, it will slam into 1st and go! It might happen at a second set of lights, but once the gearbox is warm, its fine and doesn't happen again.

Its odd and I am puzzled to know where to look! On the move the changes are smooth and without any issue. Oh, and when it does it, I have tried changing it to Park and back again and it doesn't seem to make a difference. Oh, and one time it seemed to be in 7th rather than 1st / 2nd....

I am suspecting some sort of gear sensor, wheel speed sensor or something like that, but surely it will affect it at other times. And I could just warm the car up, but getting gearboxes up to temp takes ages and I does seem a little strange to have to hang around for 10 minutes before I drive off.

Anyone got any ideas?

mudman2

When cold the system tries to warm the cats up so will use first gear instead of the normal 2

If the temp is in between normal and cold maybe its confused. The description does sounds like its do exactly what its programmed to do

offagain

It does that part OK - so if you don't completely stop, it will stay in 2nd, which is fine. Come to a complete stop and it will drop to 1st - which it says on the dials. But go to pull away and nothing happens, no gears or anything and seen it show 7th on the display! Revs rise as if it has a very high gear but simply wont really move, then bang, 1st kicks in and you are off.... and in the wet its not nice!

Its not a case of 'unintended acceleration' but a real slam in the back and jerk forward. But once its been moving for a mile or two, its fine. Seems really odd.

bigbuzuki

Transmission control unit is not selecting correct gear when cold.

Check for fault codes to zero in on the problem.

deilenberger

Madman, unlike the 955/957 series, the 958 series normally starts in first, hot or cold.

Andy E.

I believe that this problem is much more than just the transmission starting in 2nd gear. The first place that I would check would be the transmission selector switch within the shifter mechanism.

Before you start spending money on random new parts, you should scan the system for any fault codes that can point you in the right direction.

ScootCherHienie

This is POSSIBLY old or damaged automatic transmission fluid OR contamination in the valve body. I think I know what you mean by slamming into first... it's a much more violent event than any shift you have ever felt from the transmission at any other time... you may even hear a "bang" or "thud" when it finally does drop into first. The first thing to check is ATF level. If that looks OK, smell the AFT. If it smells burned, it's definitely bad. But even if the ATF still smells relatively like new ATF, there could still be something in the screen (or there may be a replaceable filter) or something lodged in the valve body. A transmission flush (this is more thorough at cleaning the inside of the transmission than just draining and refilling) with cleaning the screen and/or replacing the filter should resolve the problem unless there's damage in the torque converter or if a pump (inside the transmission) has developed a leak while under operating pressure (an internal leak, not anything you would see dripping out of the transmision). I have had this happen 2 other times with non-Porsche automatics and a transmission flush and fill resolved the issue both times. In one case, we had the problem around 90,000 miles and kept that car until it had 200,000 miles and the transmision never needed service after the flush/clean/fill done at 90,000 miles. So this could well be a fairly easy and not-expensive fix. But if the problem remains after doing the fluid flush n fill and cleaning, chances are its something inside the transmission causing the problem and since shops typically won't repair your transmission, they will replace the transmission, either with a used trans from a wrecked Cayenne or a rebuilt transmission. It's likely to cost $1000s to replace the trans with used or rebuilt. A really good shop that knows more about Porsche automatics than "replace the transmission when there are problems" may be able to narrow the problem down to a single pump that MAY be replaceable without pulling the transmission and that could be a big money saver... but finding a shop capable of that may not be easy.

bigbuzuki

Does the gear indication show correct gear when the fault happens?

When it feels like it's in 7th gear and then slams into 1st, what does the gear indication show?

Petza914

what happens if you use the tip buttons to select first at the stop during this warm up window? Any difference in sport mode?

19psi

Free reving like it's in neutral and then violently slamming into gear sounds perfectly normal to you? lol!

^^^^This right here. ScootCherHienie's advice is excellent. Google transmission morning sickness.

offagain

Ok tried a few things.

Jacked it up to see if there is anything obvious around sensors or loose wires - nothing.

switched to manual only and drove around all day yesterday and it was fine. But this morning when everything is cold and it didn't select a gear when moving off the drive. Actually showed 6th as it tried to move and was really slow as you might suspect.

moved to P and back again to manual and you can feel the gear engage and we are off, but clearly something wrong with the gear it thinks it is in.

On the point of fluid and changing it - just had it done at a local independent. So suspect it's something else there. However, they could have done something or uncovered something else. So it will be going back to them.

Just really odd, never had a car do this before and it's really strange. Anyway, thanks for the advice. I will also take a look at the selector today too, but suspect this might not be the case.

ScootCherHienie

Since this started happening right after the fluid was changed, and presumably was NOT happening before the fluid was changed... it's a fairly safe bet that something done during the change wasn't quite right. This could be something simple, like not refilling the transmission correctly... could be too much or too little automatic transmission fluid, or fluid didn't completely fill some cavity in the transmission or torque converter and while you drove it after the change, fluid finally worked into that spot but now you don't have enough ATF. Could also be that they did not use the correct type of ATF thinking it would be the same as some other Cayenne model or something but whatever ATF they used doesn't behave properly for your particular transmission model at colder temps. Or if they just did a drain and refill rather than an actual transmision FLUSH (which circulates clean fluid through the transmission before the final draining and refilling), they may have dislodged something that has now drifted into a small passage in the transmission (and there are PLENTY of small fluid paths in an automatic transmission) and blocked a passage... and that could be resolved with a transmission flush and fill also. I would research the ATF Porsche says should be in your automatic transmission then find the equivalents from some of the name brand suppliers your shop might have used (like Valvoline, Mobil, Castrol, etc.) and ask the shop what brand/type of ATF they put in your car and see how that cross-references to the ATF Porsche says should be in your transmission. If it doesn't look like a match, having the existing ATF drained and replaced with the correct ATF would likely solve the problem.

bigbuzuki

This is your smoking gun.

Maybe try resetting the power supply to the transmission control unit and engine ecu.

offagain

actually shows 1 but when it struggles to pull away in such a high gear it switches to 6 today and has been 7 before.

going to have to get it booked in to see what the problem is.

offagain

Dropped off at the local specialist this morning. Fingers crossed its simple.

But having talked to their tech first, he initial thought fluid levels, quality or maybe some sort of contamination! Funny that they jumped straight to that as a few others did.

Lets see, but they were confident that its pretty simple to fix - the fact that it seems fine when warm is a good sign they said....