Uh-oh: need advice from the experts about my tiptronic transmission

[ScottArizona]

I'm a bit worried about my tiptronic tranmission. Car is 1999 C2 tip with 65k. Transmission service performed by independent at 60k. Upshifting is great, smooth and quick, just as it always has been. Lately, however, I've noticed that downshifting, especially at lower speeds, can be very jerky, with miscellaneous clunks and thumps, as the transmission appears to be hunting for the right gear. This is most pronounced when forcing a downship (by getting on the throttle) from 4th to 3rd at low car speeds (30-40mph). The clunking, jerking, and transmission "hunting" from 4th to 3rd does not seem to happen at higher speeds or engine speeds. Also, it seems worse when the tiptronic shift map is in a more conservative mode (i.e., after I've been in stop and go traffic for a while and the car is a bit warm). Could it be that the independent botched the service and my fluid levels aren't high enough? Honestly, the transmission never felt as smooth after the transmission service, something I just chalked up to the fact that I had installed a K&N cold air intake around the same time. I'm worried...downshifting is definately not as smooth as it once was, and is downright troubling at times (i.e., after stop and go traffice tyring to induce a down shift from 4th to 3rd at low speeds).

I plan to take it back to the independent shop, but thought I'd arm myself with any info you guys might have to offer first. thanks so much. Scott.

[Izzy]

Scott, I would first get the codes with an OBDII reader. You may have an P0740 that is low fluid or low pressure. If you get codes, post back here and we can trace it further. CEL won't go on for Transmission problem. P1704 is a fault with the kick-down switch, which could be the problem too per your description

Could be Fluid is low, fluid is incorrect for car, or a pressure regulator is not working right (which was my problem at 63K miles)

The ATF has to be filled within specific temperatures or it will be wrong amount, and during the fill process it the transmission has to be moved between all gates. I got the detail instructions in the DIY section, step by step with pictures on how to do the job and the temp requirements.

http://www.renntech.org/forums/index.php?showtopic=6203

But it does sound to me like low fluid. Perhaps they filled it cold and did not bring it to temp, 30-45 Celsius.

See the list of codes below from Loren's reply (deleted my attachment to save storage space), let me know what you get and I could look up detail troubleshooting

Izzy

Edited December 7, 2006 by izzyandsue

[Loren]

The Tiptronic codes are also listed here on the site -- Tiptronic P-codes

[ScottArizona]

Awesome guys. Thanks for the suggestions. Can I get the codes at the local autozone with their reader, or do I need to take it somewhere (like a dealer) with the more sophisticated readers they have? (forgive my naivete regarding the different types of code readers). Thanks again guys.

[Loren]

Tiptronic codes are still classified as P-Codes so any reader that can do OBD II should read them. Autozone should work fine.

[ScottArizona]

Well, I just returned from my freindly neighborhood autozone, and wouldn't you know it...no codes. I'm actually kind of bummed...was hoping I'd get some codes that would at least shed some light on the problem I'm experiencing. I verified that their scanner was an OBD II device, but the employee seemed to think it wouldn't return any codes if there was not a check engine light present (I'm sure this is wrong based on Loren's above post).

So, if I have no codes, can I rule out low fluid? What could be causing this problem that would not throw a code? I'm starting to wonder if I shouldn't just take it to the dealer.

[Duke996C4]

Actually, I have had that very same problem as Scott.... luckely only once till now. Scared the hell out of me, a big clunck when forcing a downshift to pull out of traffic after low speed. I never had it again although I am a little hesitant to force it again. sometimes I am using the buttons on the wheel to force it in lower gear. I initially thought it had to do with the allwheel drive locking up somehow.

Intent to have it checked at the dealer next time I bring it in for regular service. Car has (always) been serviced by original Porsche dealership (@ 80K), and had done 85K KM's when it happened.

Car is a2 001 996 C4 Cabrio Tip.

Duke

[Izzy]

No codes could be good, potentially no torque converter issues. When I had Transmission codes the CEL never came on.

Might be low fluid. Bet you a cheeseburger that is it. First time I checked my fluid level years ago, I did it cold engine and a lot fluid came out of the fill hole. Then I drove around and it had similar behavior as you describe. Then I refilled it with some fluid the dealer gave (I brought a new 1 gallon gas can and they just decanted free ATF intno it) at the right temperature, and it was fine after that.

Do you know what kind of fluid they use, brand, type? And how much? Might be on your work order or reciept. I used almost 7 quarts for the drain, filter change, refill operation, at about 35 Celcius.

Edited December 7, 2006 by izzyandsue

[ScottArizona]

Izzy, I hope you are right. I just spoke to the independent, who has always really treated me right, and they immediately offered to check the fluid level. Their suspicions are the same as yours: probably a bit low on fluid. I hope I owe you a cheeseburger soon! Thanks again for your thoughful responses. Scott.

[Izzy]

Let us know how it turns out. My suspicion is from some practice I have observed, they get the car up on the lift, refill it, and close the fill hole. The car is up there, so the tech can not get on the seat and go through the gates for each gear for 10 seconds, like Porsche asks to do in the manual. So when you drive it, and the fluid gets to circulate, you then get low condition since the fill was not complete.

Make sure the engine is on when they are filling it, and they know the ATF is not too cold or to hot, 30-45C. Otherwise the fill will be wrong. Good luck.

[ScottArizona]

Well, here is a preliminary update: just checked my invoice and it indicates only 5 liters of atf fluid was used (approx. 5.3 quarts if I'm not mistaken). Based on Izzy's recollection that he used almost 7 quarts, I could be running significantly low! I think I'll be calling the independent shop where I had my service done tomorrow.

[Izzy]

Scott,

Sounds like the culprit. The owner's manual has 9 liters for Tiptronic ATF capacity. The 7 comes from my own drain-fill, I think the dealer can empty it 100% for the 9. But 5 or 5.3 does sound low, or done cold or the motor off perhaps.

[ScottArizona]

Izzy,

That is very interesting. I just got off the phone with the independent mechanic. He said they found the fluid "minimally low," and only had to add "a bit." As a cynical lawyer, I'm guessing this translates into "holy crap the thing was 2 liters low." What troubles me, however, was your report that the manual indicates 9 liters. My mechanic not 20 minutes ago said that his manual indicates 4.5 liters (thus the indication of 5 liters on my invoice?) What gives? Sounds like I need to try to get a hold of the factory spec so I can confirm for him.

Thanks all for the help, it has been invaluable. Loren, I'm going to join the ranks of the contributing members TONIGHT!

[Izzy]

PM going your way. The full fill is 9 in the owners manual, page 250. My local dealer uses that amount when "flushing all out". When I do it, is less than 7, more than 6. I bought 9 quart and filled the pump reservoir using 7, had some left over, maybe 1/2 quart all said and done. I used a modified pump sprayer to get the fluid up into the hole, used the other hole for a temperature probe.

[ScottArizona]

I am going to pick up the car in about an hour. However, I just became a "contributing member" and decided to peruse the TSB's, and lo and behold, there is a TSB that appears to cover my problem exactly! It is TSB 6/02, and describes how the tiptronic control unit adapts poorly to stop and go driving! Only problem is that the TSB seems to state that the problem only exists as to 02 or newer cars. The other bad thing is that if this is my problem, the fix is a new control unit and a labor charge of 130 time units (I don't even know what that means but it doesnt sound good!). I guess we'll see what happens when I pick up my car.

[norton-sp]

i know its a bit :offtopic: but im always a bit amazed that people actually drive their tiptronic 911´s in automatic :eek: ..when its so much fun changing gear with the switches..unless im stuck in a autobahn jam i wouldnt even think of it!!

[ScottArizona]

Norton-sp, I actually do manage to drive my car in manual mode a bit. However, one area where the automatic is just a hoot is slamming the pedal to the floor at about 70-80 mph and watching the car downshift to 3rd and pull STRONG at such a high speed. I've surprised a number of "faster" cars which didn't seem to be able to hang with the tip carrera given the perfect downshifts available with a tiptronic car.

On another note, car seems to be a bit better since the fluid top off, but I'm still detecting a bit of disconcerting "lurchiness." Although I haven't really driven in the conditions that seem most likely to induce the hard shifting, I've got an appointment with the dealer later this week to see what is going on. I'll keep you all posted.

[ScottArizona]

Well, I've got my dealer appt. set up for this friday, but my tiptronic woes seem to be on the increase. Today I notice a bit of "surging" or rpm "pulsing" in 5th gear, when cruising at the lower end (around 50-55 mph). At first I thought I was inadvertantly depressing the gas pedal on a bumpy road, but I have since determined that the rpm surge is not due to my lazy right foot. Also, I've noticed a bit of shuddering when attempting to pull from low speeds in 3rd and 4th gear. It doesn't do it if I try to accelerate very slowly, or if I slam it hard enough to induce a downshift. Finally, in manual mode today, shifting up from 2 to 3rd at high rpm I detected a bit of lag, almost like the transmission was slipping a bit before the car shifted up to the next gear. Maybe I'm just being neurotic but it seems like the problems are increasing. I'll update the board after I hear back form the dealer.

[Izzy]

Hopefully the dealer can extract transmission fault codes and get to the bottom of it. I wonder if you have other issues, like gunk in the inlet butterfly or valve control, based on the engine hesitation. Let us know what they tell you and get the codes printed out.

[ScottArizona]

That's so funny that you mention that. I had a dream last night that the mechanic left the instructions for the transmission change IN the transmission and that the paper got sucked somewhere it shouldn't (can you tell this problem has been dominating my thoughts? I just love this car so much, it sucks when it doesn't "feel" right). I actually wouldn't be surprised if you were right...something clogging some valve somewhere...that is exactly what it feels like (also, I had a neighbor put on his OBD II scanner last night just to ensure no codes have emerged...still clean). I'll post an update. Scott.