Tiptronic - Automatic 5th gear problem

[toos]

Hello everyone!!

I have searched the forum for a similar problem/answer, but not found any - so I'll do a post and hope for some help :)

I have a 99, 2.7 Boxster Tiptronic with approx 75K miles on the clock.

The tiptronic transmission has had an increasing "problem" lately. It started with the gearbox occasionally not wanting to shift to 5'th gear in automatic mode (at constant high speed - say 70 mph) . I then did one of two:

- I would flip the gear lever to manual, then straight back to auto, and the 5'th gear would set in - no problem.

- I'd toggle-up the tiptronic switch, the "gearmode" changed to manual, shifted to 5'th and after 5-10 seconds shifted back to auto "gearmode".

As time progressed this "occasionally" mishap turned constant - it would never get into 5'th in auto mode. It no longer helps to flip the gear lever to manual, then back to automatic - I now have to do this 5'th gear by the tiptronic switch on the wheel (it then goes into manual mode, changes to fifth, then after a few secs back to auto mode).

This is not really a BIG problem to me as I normally drive in tiptronic mode, buth the wife prefers the auto-mode - and she pointed out this "problem" to me. I'd like to adress this issue now, in fear it might increase and "worstcase" end up as a nasty repair/replace job.

Hope someone can give me some guidance to a possible source to the problem, or link me to an existing topic covering this :D

Thanks guys!!!

[Loren]

You will need someone with a PST2 or PIWIS tester to run Tiptronic diagnostics on your car.

[pompous]

Sorry to revive such an ancient thread, but ive got the same problem. There were trans fault codes (solenoid maybe...cannot recall) and the P-Car mechanic decided the transmission was bad. I replaced the trans & TC with "used" ones. All new fluid and filter at proper levels and the EXACT same thing happens still! However, there are no longer any fault codes.

Now, I suppose it could be that I bought a bad transmission and TC, but for the exact same problem to be occurring is a little odd to me. Anybody have this? Any ideas on what to do next? I'm definitely not buying another tip and swapping (that's for sure)!

[wvicary]

Its all guess work with having a diagnostic interface on the vehicle which is the PIWIS or Durametric but of greater value is someone to interpret the data.

[pompous]

There's no data to interpret at this point...I don't think. Rather, I've replaced everything, but the transmission control module and it still does the same exact thing AND throws no codes hooked up to a PST2.

[wvicary]

There is much more data then just fault codes.

[RFM]

It may sound strange, but in most cases it's only a matter of wrong wheel/tires size. Check this first before you replace Tiptronic parts.