Check for stored diagnostic codes as well:
http://www.cygnusx1.net/Supra/Librar...ection=AT&P=13
When you get the fluid changed make sure the transmission fluid cooler is getting flushed too. I can recall if there's a thermostat on it or not, if there is the cooler won't get cleaned out unless the fluid is hot or the thermostat is stuck open (another possible issue).