Quote:
Originally Posted by rjahl
What makes the OP think the trans overheated? Did he get a warning on in the Kombi? I'm pretty sure the trans overheat will just lock you into a gear and throw a gear warning light without a power cut.
I would not change to a high temp fluid. The transmission is designed for a specific fluid with specific friction coefficients and viscosity. Anything other than OEM fluid will not work correctly. In any case, it's the hi temps you need to avoid. I do recommend changing fluid every 50,000.
Before I modified anything, I would check to insure that the cooling system is working like it should. I'm pretty sure you have a trans cooler built into the radiator and take note that there is a thermostat in the radiator that controls the trans fluid temp.
Regarding the trans tune , I've learned a lot about the ZF transmission and one item of recent discoveries me is the Torque Converter Clutch operation. It seems like the TCC spends a crap load of time in a "modulated" mode where the clutch is only partially engaged. Any constantly slipping clutch can build up a bunch of heat that the cooling system will need to deal with. One of my next experiments will be to lock up the TCC sooner and try for a full time TCC lock up in manual mode.
Recent logs in my Z4 show the TCC never locked up through a full 0-80 MPH WOT run that included 7,100 RPM shifts. Normal driving in 6th gear have the TCC in modulated mode up to 2,500 RPM where it registers a full lock up.
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I don't know that the transmission overheat always throws a code.
tetsuo111 had issues where his car would cut power without any indication as to why, and it's something I've seen a few 335i guys speak about.