986 Tiptronic gearbox - problems with 3rd gear
 

My car has developed a weird issue over the last week. All of a sudden when in drive, once 3rd gear is selected my car judders (like the rear wheels are struggling for traction) for a few seconds and then all is fine until the next time 3rd is selected. This happens most frequently on slight inclines/hills and under very light acceleration (harsh acceleration there are no issues).

I cant see this being a sudden issue with the tyres - its fine in every other gear and the car is already moving at around 30mph when it switches to 3rd and then judders. The tyres have good tread left, are the wider 265 size and have decent Bridgestone N rated tyres at the correct pressures.

The gearbox oil was changed just over a year ago at the dealership so also can't see this being the cause. I'm sure it has to be gearbox related though as it happens 95% of the time in 3rd gear and the other 5% in 4th (but its much more subtle in 4th).

It happened last night quite violently, on a completely flat surface, in the dry and once again I was already travelling at about 20mph when it switched to 3rd and I barely accelerated at all.

I've tried switching between 3rd and 4th in manual mode and cant get the problem to occur at all, which is also leads me to believe it surely has to be gearbox related.

Thanks for any help with this. I'm taking it to a Porsche specialist tomorrow but was interested on people's opinions on this. The fault is hard to explain, but the best way to describe it is like juddery wheel spin/loss of traction, but at slow cruising speeds, under light acceleration, when switching to 3rd gear. I did find wet roads a few nights ago did also exaggerate the issue. I've had this car for 2 years though, driven it in all conditions and never had this issue which now won't go away.

Edit: This is a 2000 2.7 986 with no traction control

Hey Eliot

Try disconnecting your battery for 10 minutes. The tip adapts and have quite a few shifting maps, or patterns if you prefer. Wouldn't be surprised it only needs resetting. Be consistent with your driving when you'll have it reset & test.

If a mechanical issue (ultra rare btw) you can be sure you'll have a CODE reg. See if you can pull the codes out with a durametric or a generic code reader.

Tip
 

I would be checking fluid levels.

Thanks for the replies. Sadly I already tried a battery disconnect. I also haven't noticed it throwing the gearbox warning light (flashing between P/D etc and 4) but will try and get it fault scanned regardless. Fluid levels may be a good idea too as it was leaking a year ago, the dealership supposedly replaced the gasket to fix this and refilled the oil. Haven't noticed any leaks but still may be with a check

It's an odd beast that tip. Mine does what you describe but only in 1st when on starting on a hill. No codes,no leaks, fluid level is fine. I replaced the electric harness inside the pan 2 years ago when I was getting the D-4. Transmission works fine in manual mode flailing through the gears on the track, just that one little gremlin. Keep us posted on what you find. Note that fluid level is important and sometimes needs to be adjusted ( read topped up) after a fluid change as the ATF works it's way through the system.

Ah, you did the battery/reset thing already. To be honest I know very little about those tiptronic but somehow I have a feeling it is management related. As in software.

Saying that; with all of that management & controls that the tiptronic runs onto, seriously, I can't think of any possible way that a gear could have been damaged. Unless originally faulty from factory then, unfortunate mate :/ Feel bad for you because that is not going to run cheap, removal inspection alone. That (@dealer) might runs you more than simply finding a second hand + swap at your local indy shop. Investigate that before (get quotes)

Raised by NewArt, that manual mode might be a little bit more forgiving - have you tried? If you are not having issues in m-mode, my advice is buy yourself one of those padle wheel (by RAID) and keep it on m-mode. Personally I can't recal when was the last time I've driven the car in auto mode mate, must have been in 2009 or something (when I got the wheel).

http://986forum.com/forums/uploads01...1381469734.jpg

That steering wheel looks awesome! The specialist I went to see this morning said pretty much what you guys have been saying. It didn't play up once typically when he took it for a drive, but he was saying that he didn't feel it was a mechanical issue (if he was to take an educated guess) as it's so rare that these gearboxes have mechanical faults and if it was as such, he wouldn't expect the issue to come and go. He was also leaning towards an electronic fault (perhaps the control module) and said when he gets his fault scanner back next week we can try and scan it then. I'm going to try a battery disconnect again and this time leave it for longer and just see if that does anything.

Hi,

this transmission adapts itself. Means it takes care of how the drivers is driving and adapts this to his programm. This is what can be resettet easily. But i think that won't help in that case.

Below that layer is an overall adaption. This adaption can be earased and relearned by driving sequences. But this is not a simple task and can't be done without a PIWIS system.

Best would be to diagnose the AT with PIWIS and check if there are AT parameters out of specs.

Also i would recommend to check the ATF level. And always do a ATF and ATF filter change with every oil change, because the AT has 12 litres of oil but you only change 4 litres, so you only dilute the oil.

Regards, Markus

My SWAG is it's a torque convertor issue and recommend you take it in for a second fluid and filter change. Unless a pressurized system of flushing is used you still have old fluid in the trans and particularly in the tc.:cheers:

The tiptronic 'clicks' so much faster when old ATF is installed. Thinner works. Goes up to operating temp much faster also. See, advantages loll

Dealer pressurize, flush all, clean/filter and reseal. They also provide an Apocalyptic-like billing paper at the end of it :/ Ask me how I know. (Hard to find any porsche recommended/specialized fluids around here. Dealer it is for these sort of things)

I'd really like to see how you "pressurized flush" one of these transmissions..

According to the german Porsche forum and Tim Eckard who invented a presuized flush system the 986 and 986 AT ATF can be flushed with the engine and transmission in the car. But it is not that easy to do. Tim Eckart offers special adapters for his system. Start

Tim Eckart is like Jake but for pressurized ATF flush systems over here in Germany.

Regards, Markus

Unfortunately, that is a fluid exchange system, not a pressure flushing system. Exchange systems adds fluid to a running transmissions as fast as it drains out, which is in fact not even as good as simply drain and refilling the transmission multiple times, and end up wasting large amounts of fluid, which why they are not widely used in North America because they are expensive to buy, waste fluid, and do not do a better job than a simple drain pan and a wrench. Because of how they work, exchange system mix the dirty and clean fluid, requiring using a very large volume fluid to be exchanged to get anywhere near where a true pressure flushing system, which pushes the dirty fluid ahead of the clean, much like the way a pressure brake flushing system cleans out the brake hydraulics with only a minimal amount of new fluid.

Porsche Tiptronics have no external transmission fluid lines, preventing any pressure flushing, only draining and refilling.

I recall we went through this argument about pressurized fluid changing systems before and someone proved it can be done and provided links to the equipment to do it so perhaps if you use the search feature here you'll find it. Having to change your trans fluid three or four times to get "new" fluid in is ludicrous.

I believe you recall incorrectly. This is the layout for the transmission cooling system as used on the Boxster Tiptronics. All of the lines in the diagram are coolant or vacuum lines, none carry transmission fluid, making it impossible to connect a true pressure flushing system to the Tip and push out the old fluid with the car assembled (you can barely even see the cooler on the car, much less get at it to connect anything, and there are no external pressure ports on the gear box) :

http://www.scuderiacarparts.com/imag...JCHJZ9GTGA.gif

Over the years, several companies have claimed to have developed a pressure flushing system, all of which turned out to actually be exchange systems, which mixed the old and new fluids during the process, making it inefficient.

Hello JFP in PA,

never have seen in it person how it was done on a 986/996. As far as i understand from the readings in the german Porsche forum they use the oil cooler lines to do it on the 986/996.

Also you do not need a pressure system if you AT oil pump generates enough pressure to forward the oil. And i'm not convinced that a pressurized system is better in any ways, because you use an overall higher pressure that is normal in the system. As you know how the EHS works and that you are not allowed to clean it with pressurized air for example, i'm not shure if it is a good a idea to use high pressure at all at this AT.

As you know there are several manufacturers that at that time used the "life time" fillings on their AT transmissions without a torque converter drain plug.

Mercedes-Benz themselve uses the Tim Eckart system and a very similar exchange system like Tim Eckart in their german workshops for their cars of that period with no torque converter drain plug. Might not be that efficient, but works. And better to change the ATF this way than change the complete AT under warranty, because many cabs over here in Germany are Mercedes brand and the Mercedes AT 772.6 just failed in that cab cars within short time when the ATF oil wasn't changed. So they reduced from life time filling to a 60 TKm complete ATF change interval including ATF oil filter.

And yes, you need around 12-13 litres of ATF to change a 8.5 litres MB 722.6 AT system with that method. But you can exchange the whole ATF in that way, while else you can only dilute when you cannot flush the toque converter.

So the real problem with this MB lifetime filling AT is you don't have a drain plug on the torque converter. I think this is the same with the 986 ZF AT, which is also very very similar constructed to the MB 722.6 AT.

But i think we have discussed that already. So i don't want to be annoying. Maybe there are just different kinds of views how to solve the problem. Think you agree that the idea of a lifetime ATF filling doesn't work as initially intended by the car and transmission manufacturers in practice.

Regards, Markus

Eliot, apologies if my initial comment made your thread derived from a question to a technical quiz! Still looking FW to see if you have any fault code(s). Let us know when you have them.

As for the dealer ATF flush, I have no idea how they do it and couldn't care less in all honesty. They do not charge by liters as qty does not appear on the billing. Mind you the Porsche service center here is larger than your average WallMart mall with 100+ employees hard at work. All of the fluid/filling hoses runs down from the ceiling, so my guess is they don't really bother with opening little cans of ATF all day long lolll

They do however bill/list for a complete flush and a 'certain' cleaning fluid and take the car for a spin twice in the process.

The Damage: $532 (in green dollars equivalent!).

Markus, I have no idea if the tool they use is the same as Tim's kit. They did removed a few parts from the tiptronic and I saw them plugging all kinds of stuff to it, whatever they are. Couldn't see clearly from the service center waiting room - was busy reading the HD pictures out of those amazing Porsche books instead ;)

For anyone' interest, this was done to troubleshoot an inconsistent slipping of the 4th to 5th gear when tiptronic was hot. A problem that my tip had developed at the time.

That problem never occurred again after the ATF service.

As mentioned earlier, there are no external oil cooler lines carrying ATF fluid on the Tip, so it is not possible to attach any system to the car. The cooler itself is also nearly inaccessible with the car assembled.

As for pressure, the normal internal operating fluid pressures of the Tip and most other automatic transmissions is in hundreds of PSIG; a service pressure flushing system runs at a fraction of that normal internal pressure, so there is absolutely no possible damage to the internal component's of the gear box when the flushing unit is operated properly.

Years ago, manufacturers discovered that drain plugs on torque converters create weak spots in the unit that lead to cracking or worse, particularly on higher horsepower vehicles, or with engines that operate regularly at higher RPM's. As such, they removed the drain plugs, and now no one I am aware of has them anymore, and is also why most shops went to pressure flushing systems in the first place.

At the shop, we don't wait until the ATF in the Tip reaches ink like conditions of the factory recommended service intervals before draining it, preferring to shorten the normal service intervals to around 40K miles for normal street cars, sooner for cars that are tracked. By replacing at least some of the fluid regularly, the dilution effect helps remove the normal debris and beat up fluid that accumulates over longer service intervals, usually eliminating the need to fill/run/dump the fluid multiple times to clean the system out; and this also lowers the overall "life of the unit" service costs as well.

I feel cheated. That’d be unfortunate because I really like going to my Porsche center here. Fresh, new construction, modern lighting/everything, stunning beautiful and caring staffies. The Expresso machines with imported Columbian, the thick paper books…. man those pictures…. oh you should see this fast-cars stuff. Refined ecstasy ;)

I’ll be at Porsche the following week to pickup a liner & oil thing cooling scoops I’ve ordered (plastics!). I’ll ask our resident service mgr for you… I bet he’ll tell me vacuum instead of pressure.

Interested with the 20k range hydrocracked group III and V oils only mate. What you call "ink" ;) All the the rest is a scam if you ask me. I'm sure even peanut butter oil would work in our cars lolll

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