@ Tapani.. & 1986 Nate
I know what you mean about the heat from the TC being unlocked would seem to outweigh the benefits of the additional flow, but according to Subaru,
"ATF Temperature Sensor
When the ATF is hot (AWD only), the TCU shifts the transmission as if in the
POWER mode. This pushes the shift points higher which allows the engine to run faster. The oil pump then circulates ATF through the oil cooler more quickly so as not to overheat the engine coolant."
It would seem that the concern was engine coolant temp, perhaps the issue was localized boiling? And how to tell if it is indeed running in power mode if it's a newer one with no "power" light in the dash? Power mode would seem to exclude 3rd gear lock up.
A partially plugged filter might be a contributing factor.
It would also seem that not all TCUs' are created equal... Tapani's won't lock up below 150F. Both of mine will lock up from a cold start within a kilometer if it's 50F outside or warmer. But, neither of them has ever locked up in 3rd gear. Ever.
Just wondering.. since mine's never done it, when the TC locks up in 3rd, does it shift into 4th locked up, or does it unlock, shift into 4th and then lock up again a bit later?
an interesting read..
http://www.northursalia.com/techdocs...ssion/4eat.pdf