Tiptronic Problems HELP

Hi all, New to the forum, and sadly my first post is about a problem.... I know everyone likes a good technical conundrum though, and i'm desperate for a but of advice. I have posted this thread on another 996 forum, but haven't found anyone with any ideas yet.... Just purchased a 1998 996 tip and I'm already experiencing problems with the tip box, which I suspect is quite serious. Would really appreciate any opinions! It started as a fairly mild blip in 2nd gear. The car pulls away fine, upto about 2500 - 3000 rpm, and then under constant throttle pressure it feels like the car tries to change gear. The revs dip 300rpm or so, you can feel a noticeable 'donk', especially before the car is fully warmed up, and then it resumes normal progress. It really does feel like a gear change, but it definitely isn't. It also only occurs in 2nd gear, always at a similar point rpm/speed, and is much less pronounced when the car is fully warmed up. So... I took the car to a specialist for a transmission fluid and filter change... nothing else. And it has come back twice as bad as it was. The donk in 2nd is still there, just the same, but in addition it has now started to slip / miss a gear completely!!! Every now and then at very low speeds, the car will suddenly rev freely for a second, like it's in neutral, and then 'catch' a gear, jerk a bit, and carry on like nothing happened. It has done this two or three times now and I don't feel I can drive the car any longer incase more damage is caused. It feels obviously as if the crank is not connected to the gear box, which I am guessing is something to do with the Torque Converter or valve body. Not sure if Porsches have any friction plates or anything similar which could be slipping without enough oil. When I first left the garage it slipped twice whilst going slowly over speed bumps, so I wondered if it was related to the car being tilted a little starving the torque converter of oil?? It has also stalled once in Drive whilst stationary. I was sat waiting for another car to do a 12 point turn. I was in D, on the brake, and after 30 secs or so the revs wobbled and it just stalled. Any thoughts or similar experiences anyone? Someone on the other forum I mentioned said that..... "When setting off in second gear, the car adjusts the torque converter itself, so when you set off it is in a slightly different gear (1st) and as you say you feel the car adjust into 2nd, while all the time showing 2nd on the dash." Is this true? If it is my OPC is not aware?? Yours desperately. A.

I'm not that well clued up on tiptronic boxes (even though I have one) but it does sound like a torque converter or fluid level problem. Mine feels like it has a 2 1/2 gear smetimes when accelerating in second, and at about 2500rpm the revs will dip, as iif it has found another gear. No noises at that point though. Whether or not I am correct I don't know, but I put this down to the lockup clutch in the torque converter reaching the point at which it stops slipping. If you look at the engine speed versus road speed graph (in your owners manual) you'll see a curve at the bottom of the graph for 1st and 2nd gears where the revs vs. speed is not linear. I think this is what gives the strange sensation, that the "other forum" member may have been describing, but using the wrong terms. Was the independent a known specialist? Checking and filling the tiptronic transmission is a tricky (and messy) job. The fluid has to be up to operating temperature with the engine at idle, and the level has to be topped up until the fill tube starts to overflow. Also, using the wrong fluid will screw things up completely and do permanent damage.

Hi Andy, Sorry to hear your having problems with your new car. I have a 1998 996 C2 Tip which I have had for about 3 years or so. Last year I notice that in 2nd gear it would sometimes seem to 'hang' in gear and also when changing up (not at high speed - just regular conservative driving) it would appear to slip the clutch (even though it doesnt have one as such) but then change up. Sometimes with a bit if a clunk. I took it in to OPC and they couldnt diagnose the problem unfortunately. Also, Tiptronic boxes werent serviceable via an OPC. I left it like that but then I had a seperate, or so I think, Basically I would hear a banging from the rear when cornering hard or over a bump. This worsened. I took it to OPC and it was diagnosed as the rear differential had failed. They replaced the box/diff as a complete unit under warranty. Also, some on the lectronics are different and to change the box to a new one you need to upgrade the control unit or something. I wouldnt imagine that my diff problem and the problem you and I had were the same but the box problem hasn't occured since. I dont wish to be negative as I love my car to pieces but would reccomend that you invest in an OPC warranty if you havent already got one. You need to go to a dealer, spend £100+ on a 111 point check and then if it passes you have a OPC warranty with RAC eqv. There are plenty of threads on OPC and non OPC warranties on this site. Obviously if you car was bought from a dealer and/or you have a warranty then you should be covered to some degree. Good luck and enjoy your car! Rob

Beershark, thanks very much for your response, I am very interested in your experience with the rear diff. no one has suggested before that that may be the problem with the slip/clunk in 2nd gear before. I have spoken to a few people with a very similar experience, and they have all been unable to get it diagnosed. I believe I now have two seperate problems, the original issue in 2nd as you describe still remains, but I now have a new issue that appears to have been created by changing the transmission fluid. With hindsight I could have lived with the initial problem, but the since changing the fluid the car is now virtually undriveable, and I'm very concerned that I might do more damage everytime it slips. Richard, I took the car to Chelsea Carrera. They were recommended to me by someone on pistonheads, and they are also very conveniently located for me. I could not imagine that changing the transmission fluid could be particularly difficult, or that it could lead to such problems. What exactly can happen if you don't do the repacement properly? Can you get air in the system? Could that cause the car to feel like it is missing a gear like it is? I'm really not sure how to address this now, should I go to another specialist (I'm thinking JZ Machtech this time) and get the fluid changed again?

I was just concerned that the level was correct - not underfilled, which could cause the problems you are having. If it was J Bloggs Porsche and Trabant specialist, I would be tempted to ask if they knew the correct filling procedure, but Chelsea Carrera should know what they are up to. What do they think is the problem?

So... I took the car back to Chelsea Carrera and they did end up having to 'top up' a small amount of transmision fluid. Apparently, they couldn't connect to the diagnostics system when they did the original job, which is necessaary to get the levels right. The major concern I had is now resolved, but I still have this strange 'gear change' feeling in second gear. I managed to get an engineer from JZM on the phone to discuss this though. He said it was most probably the clutch plates in the gear box beginning to slip, and coudn't see any possible connection with the rear diff. it locks out after about 2500rpm in 2nd, and never does it again? He suggested that a gearbox re-build is the only answer, a full weeks labour plus any parts...ouch!

The 2500rpm "change" in 1st and 2nd gears is NORMAL, like I said in my earlier post. That is the speed that the CLC (converter lockup clutch) locks up. You don't tend to notice it in 1st, but it is there. When filling, you have to plug in the PST2 to read the transmission fluid temperature. I expect it was too cold when they filled it the first time.

Andy, Have you thought about trying the air flow sensor advice given on the thread you posted on Pistonheads? Try cleaning the MAF (see link), it's a no cost effort, and it may cure the problem. http://www.6speedonline.com/forums/showthread.php?s=&threadid=34434&perpage=15&pagenumber=1