1999 996 TIP Problem - Any Advise

I am the original owner of a 1999 996 Conv Tiptronic. When I am in automatic and on the freeway the tranny surges/searches between 4 & 5th gears. When drive in manual and shift on the steering wheel it is fine. Any ideas or solutions or anyone out there with the same problem?

Change the trans oil and filter. The Boxster S on this episode of Wheelers Dealers had the same problem. They fixed it with a new filter and new trans fluid. http://thepiratebay.se/torrent/82504...TV.x264-SM.mkv

Need more info to help you. How many miles on the car/trans, any previous work done to the trans, have you had the trans serviced, etc?

Have you checked if it's thrown any codes?

No codes. Car has 170k miles, Engine rebuilt 70k miles ago, Transmission Service about 30k miles ago.

Shifting in these transmissions is controlled by solenoid valves. Shift points are determined by many things such as speed, accelerator position, which one of the five shift maps the trans is currently in, engine and trans temperatures, etc. The problem could be in the solenoids, any of the sensors for the items noted above. Or, the trans could be low on fluid, incorrect fluid used, dirty trans filter, etc. I think I would start with a check of the fluid level. If that's good, perhaps another service with new fluid and filter. I don't know what the consensus is on the number of miles one can expect with this trans, but they have a reputation for being durable. You might check on the Boxster 986 forum for threads that discuss tiptronic issues as many Boxster owners seem to pile on the miles.

Quotes source post: 11775629

Forgive me, I can't seem to get past your first sentence. :wow:

Quotes source post: 11776118

Are you sure there are no transmission error codes? The CEL would not be on and it takes at least a Durametric to read these codes. If you are sure there are no codes, and if you are sure there are no diagnostics that a Porsche tech could perform on the transmission with the Porsche diagnostics computer, to possibly ID a replacement component, then a fluid/filter service is I think your only option. While 170K miles is not that many miles on a Tip they can wear out. Generally they do so when they do not receive timely fluid/filter servicing. The thing acts up and in a desperate move the Tip fluid/filter service is done. This might improve things for a while. Or in some cases the fluid change can appear to accelerate the Tip's demise. 'course, there is no way of knowing how the Tip would have behaved had it not had the fluid service. You can have the Tip fluid/filter service done and cross your fingers. Or before you do this you could consult with a reputable transmission shop in your area to see what the shop recommends. If the Tip is bad do not run it too long. These are rather common transmissions - in one form or another (they are made by ZF) -- and they can be rebuilt and for not large sums of money provided you don't run the transmission into the ground. Porsche techs I have talked to about this tell me they sometimes have a car brought in with instructions to remove the Tip and send it to a transmission shop for repair and then once done to re-install it back in the car.

There should be soft codes in memory if you're experiencing something as bad as slipping. I have a wonky solenoid which is no biggie as I use it in manual mode 99% of the time. I've met more people who have a fluid change and soon after something really weird happens that it suggests to me its more then coincidence... The choice is really a rebuild by a specialist who is very familiar with the ZF and Chrysler (during the Mercedes era) built Tip's. I have a guy lined up through my indy that when I have really big problems the Tip will come out to be sent off. My quote was $6K in and out and back in. (tx extra). The problem with the solenoid function is that they are internal - not external. Your avg indy (and dealer) just won't touch them other then a new filter and juice. There is just so much that can go wrong - they don't need you coming back in a week with more problems requiring the unit to be dropped again. The re-builders have a whole jig set up and are able to test the unit before they send it back so their confidence that its going to work is pretty high which is why the cost is so high as they have to be thorough. The upside: if you don't want to spend the money right now on a rebuild - keep driving it in manual mode - by doing so you bypass the TCU map program that is attempting to command the faulty solenoid. Eventually, you/me will have to bite the bullet and do a R&R. If you experience slippage while in manual mode when you use the gas - then you have a torque converter issue and that is only cured by a rebuild.

I am always the one for the easiest solution first. I did see the Wheeler Dealer episode where a change of filter and fluid cured their problem. I would DIY that part first then tackle the other suggestions if that doesn't work.

Quotes source post: 11782622

There is an 'opinion' concerning people waiting too long to change the fluid and *then* really large issues result after they go ahead with a change. Seems to be a roll of the dice. It doesn't help that you get different opinions from dealers and indy's whom say the fluid is a 'lifetime fill'. I frankly don't believe it. Either change the filter and fluid every few years (which is expensive as that fluid must have platinum in it!) or let it go and do a rebuild later. Pay me now or pay me later. I'm in the later position and I'm fine with that. I rather suspect these Tip units are 'lifed' as everyone I've come across whom have shifting issues all have medium to high mileage.